-NRLF 


UNIVERSITY  OF  CALIFORNIA 

ANDREW 

SMITH 

HALL1D1E.: 


J 


' 


Modern  Machine  Shop  Tools 

THEIR.  CONSTRUCTION.  OPERATION 
AND  MANIPULATION.  INCLUDING  BOTH 
HAND  AND  MACHINE  TOOLS  ^  ^  ^ 


AN     ENTIRELY     NEW     AND     FULLY     ILLUSTRATED     WORK, 

TREATING     THIS     SUBJECT     IN     A     CONCISE 

AND     COMPREHENSIVE    MANNER 

A    BOOK    OF    PRACTICAL    INSTRUCTION 

IN    AI.L  CLASSES   OF    MACHINE   SHOP    PRACTICE 


Including  Chapters  on  Filing,  Fitting  and  Scraping  Surfaces  ;    on  Drill? 

Reamers,     Taps   and   Dies ;     the   Lathe  and   Its   Tools ;     Planers, 

Shapersand  Their  Tools;  Milling  Machines  and  Cutters;  Gear 

Cutters  and  Gear  Cutting  ;  Drilling  Machines  and 

Drill  Work  ;  Grinding  Machines  and  Their 

Work  ;  Hardening  and  Tempering; 

Gearing,  Belting  and  Trans- 

OF  THE  r   \ 

mission  Machinery  ; 

Useful  Data  and 
Tables 


UNIVERSITY 

By   WILLIAM    H.    VAX    DERVOORT,    M.E 


Illustrated  by  673  Engravings  of  the  Latest  Tools  and  Methods, 
all  of  which  are  fully  described 


NEW   YORK 

NORMAN   W.    HENLEY   &   COMPANY 

132  NASSAU  STREET 

1903 


1-1 


HALUDIE 


COPYRIGHTED   BY 

W.    H.     VAN   DERVOORT 

1903 


Composition,  Printing,  and  Electrotyping 

By  MACGOWAN  &  SLIPPER 
30  Beekman  .Street,  New  York,  U.  S.  A. 


PREFACE. 


This  book  is  the  outgrowth  of  a  series  of  articles  prepared  by 
the  author  for  the  students  in  machine  shop  practice  at  the  Uni- 
versity of  Illinois;  some  of  these  articles  having  recently  been 
published  in  ''Machinery."  An  effort  has  been  made  to  treat  the 
subject  in  a  clear  and  comprehensive  manner,  carefully  avoiding 
all  unnecessary  matter  and  presenting  to  the  apprentice  and 
mechanic  many  points  pertaining  to  the  tools  with  which  they 
come  in  daily  contact,  and  about  which  they  are  often  unable  to 
obtain  all  the  information  necessary,  in  order  that  they  may  use 
these  tools  correctly  and  efficiently. 

In  treating  on  the  various  classes  of  small  and  machine  tools, 
the  author  has  endeavored  to  bring  out  much  pertaining  to  the 
construction  and  care  of  these  tools,  as  well  as  upon  their  uses. 

The  importance  of  the  machinist  having  at  least  a  limited 
amount  of  information  on  the  subjects  of  Fastenings,  Gearing, 
and  Belting  and  Transmission  Machinery  has  prompted  the  addi- 
tion of  chapters  upon  these  subjects. 

The  author  wishes  to  acknowledge  his  indebtedness  to  the 
publishers,  the  Industrial  Press,  and  the  tool  manufacturers,  who 
have  so  kindly  assisted  him  in  getting  together  many  of  the  illus- 
trations and  tables  used  in  this  work. 

March,  1903.  W.  H.  VAN  DERVOORT. 


116602 


INTRODUCTION. 


The  correct  manipulation  of  metal  working  tools  comes  per- 
fectly natural  to  many  of  our  young  mechanics,  and  they  easily 
become  expert  in  their  use.  It  seems  to  be  born  in  them,  and 
they  make  good  workmen  no  matter  how  poor  the  tools  with 
which  they  work  and  how  bad  the  instruction  they  receive ;  but 
where  one  such  man  is  found  there  will  be  a  dozen  others  who 
can  acquire  the  necessary  skill  to  be  called  good  machinists,  only 
after  careful  study  and  close  application  of  the  most  thorough 
instruction.  The  time  required  to  accomplish  this  will  depend 
entirely  on  the  man  and  the  conditions  under  which  he  works. 
Under  favorable  circumstances  two  to  six  years  will  be  required. 
The  more  the  apprentice  reads  and  thinks  the  more  quickly  will  he 
master  his  trade.  Every  apprentice  should  be  a  regular  sub- 
scriber to  at  least  one  good  paper  treating  on  the  subject  and 
should  READ  it.  He  should  never  fail  to  look  over  the  advertising 
pages  of  each  issue,  as  these  pages  constitute  a  perfect  index  of 
progress  along  the  line  of  his  chosen  occupation.  The  reading 
will  create  thought,  will  broaden  the  ideas  and  put  the  young 
man  in  a  better  position  to  appreciate  what  he  sees  and  hears. 

The  young  machinist  must  keep  constantly  before  him  the  two 
requisites  of  a  good  mechanic — accuracy  and  rapidity.  The  first 
he  must  acquire,  and  if  he  would  succeed  in  these  days  of  close 
competition,  he  must  couple  with  it  the  ability  to  produce  such 
work  quickly.  He  should,  above  all  things,  train  his  judgment, 
having  it  continually  with  him,  and  should  learn  as  quickly  as 
possible  the  strength  of  the  materials  with  which  he  is  to  deal. 
This  will  come  more  by  experience  than  by  calculation  and  let 
good  judgment  and  common  sense  aid  in  making  the  experience 
bill  low. 

"Observation  is  a  great  teacher."  Therefore  he  should  learn 
to  observe,  noting  carefully  the  ways  in  which  the  skilled  me- 
chanic performs  his  work.  His  thoughts  must  be  kept  contin- 
lially  on  the  work  in  hand,  studying  better  and  quicker  ways  to 
do  it.  He  can  gain  the  confidence  of  his  employer  in  no  better  way 


12  INTRODUCTION. 

than  by  strict  attention  to  his  work,  careful  observance  of  all 
regulations  pertaining  to  the  management  of  the  plant,  and  a 
sincere  disposition  to  do  at  all  times  his  very  best.  He  should 
be  perfectly  free  to  ask  questions ;  sensible  ones,  as  the  other  kind 
will  injure  his  cause.  He  must  be  cautious  about  making  sugges- 
tions as  they  are  usually  not  thankfully  received.  When  the 
foreman  gives  precise  instructions  as  to  how  to  perform  a  piece 
of  work,  the  instructions  must  be  followed  to  the  letter,  even 
though  he  thinks  he  can  do  it  in  a  better  way.  He  is  probably 
wrong,  but  if  not  the  opportunity  to  do  it  his  way  will  come  soon, 
and  in  such  a  way  as  to  please  rather  than  provoke,  by  proving 
the  better  method. 

He  must  learn  to  take  a  hint,  as  the  foreman  may  at  times 
suggest  rather  than  tell  him  that  it  would  be  best  to  do  the  other 
way;  and  above  all  things  he  must  not  have  to  be  told  a  second 
time.  It  is  bad  to  duplicate  accidents  to  tools  or  mistakes  on 
work,  and  especially  so  when  previously  cautioned  on  these 
points. 

He  cannot  be  too  neat  and  orderly,  not  only  with  his  tools  and 
work,  but  in  his  personal  appearance. 

The  young  mechanic  should  never  lose  an  opportunity  to  visit 
other  shops,  as  he  will  be  sure  to  get  some  good  ideas  from  them. 
More  can  often  be  learned  in  some  poorly  equipped,  ill-man- 
aged concern  than  in  a  shop  running  under  the  most  perfect  sys- 
tem, as  we  are  often  more  forcibly  impressed  with  the  how  not  to 
do  it,  than  with  the  how.  A  careful  perusal  of  the  trade  cata- 
logues issued  by  all  the  leading  machine  and  small  tool  builders 
cannot  fail  to  be  of  value,  as  in  those  catalogues  will  be  found 
many  excellent  cuts,  with  description  of  tools,  and  often  valuable 
hints  on  their  manufacture  and  uses. 

Mechanics  who  learned  their  trade  before  the  introduction  of 
modern  tools  and  methods  frequently  fail  to  appreciate  the  im- 
portance of  their  making  an  effort  to  familiarize  themselves  with 
the  nicer  points  of  detail  of  the  later  small  and  machine  tools. 

The  successful  working  and  tempering  of  high  grade  steels 
and  the  methods  of  grinding  now  employed  have  been  the  principal 
factors  in  the  successful  manufacture  of  the  many  excellent  small 
tools  now  in  use.  Better  tools,  better  methods,  better  workmen 
and  the  best  of  mechanical  ability  have  evolved  from  the  ill- 
designed  and  inefficient  tools  of  but  a  few  years  ago  the  excellent 
ones  of  to-day. 


INTRODUCTION.  13 

Many  mechanics,  both  old  and  young,  fail  to  appreciate  the 
finer  points  in  a  good  tool ;  they  fail  to  realize  that  every  line, 
curve  and  angle  in  its  construction  represents  the  most  careful 
study,  and  in  most  cases  have  been  arrived  at  only  after  years  of 
experimentation. 

In  taking  up  the  subjects  pertaining  to  machine  shop  tools, 
their  construction  and  uses,  two  general  subdivisions  may  be 
made,  small  tools  and  machine  tools.  Under  the  head  of  small 
tools  may  be  placed  all  hand  tools,  measuring  tools,  cutting  tools 
used  in  machine  tools  and  jigs.  The  subdivision  of  the  work  com- 
monly performed  on  metal-worKing  machine  tools  may  be  briefly 
outlined  as  follows : 

First — Turning  and  Boring ;  as  performed  in  the  lathe,  screw- 
machine,  turret-machine,  vertical  boring  mill,  etc.,  in  which  the 
work  is  usually  made  to  rotate  to  a  cutting  tool  or  tools  which, 
aside  from  feeds,  are  stationary.  This  operation  usually  pro- 
duces curved  or  circular  surfaces,  both  internal  and  external,  but 
may,  as  in  facing,  produce  a  plane  surface. 

Second — Planing  Operations ;  as  performed  on  the  planer, 
shaper,  slotting  machine  or  key-way  cutter,  where  the  work  is 
given  a  straight  line  motion  to  a  stationary  tool,  or,  as  in  the 
three  latter  types  of  machines,  the  tool  is  given  a  straight  line 
motion  over  stationary  work.  In  the  former  case  the  feeds  are 
given  to  the  tool  while  in  the  latter  the  work  usually  receives  one 
or  both  of  the  feeds.  In  the  case  of  the  traverse  head  shaper, 
however,  the  tool  is  given  both  feeds  over  perfectly  stationary 
work. 

Third— Milling  Operations ;  as  performed  on  the  various  types 
of  milling  machines  where  a  rotating  cutter  produces  plane, 
curved  or  formed  surfaces  on  the  work,  the  latter  usually  receiv- 
ing the  feeds. 

Fourth — Drilling;  the  forming  of  circular  holes  in  solid  stock 
by  means  of  a  revolving  tool  at  one  operation,  the  tool  usually 
receiving  the  feed.  Drilling  differs  from  boring  in  that  the  latter 
term  applies  to  the  enlarging  and  truing  of  a  hole  already  formed. 

Fifth — Grinding ;  these  operations  involve  the  removal  of  metal 
and  finishing  of  the  surface  by  an  abrasive  process,  the  material 
being  ground  rather  than  cut  away.  The  universal  and  surface 
grinding  machines  correspond  with  the  lathe  and  planer,  a  rotat- 
ing wheel  of  emery  or  corundum  taking  the  place  of  the  cutting 
tcol  fn  the  latter  machines.  Grinding  operations,  although  IICLCS- 


14  INTRODUCTION. 

sarily  slow,  make  possible  the  accurate  finishing  of  the  hardest 
metals. 

The  scope  of  this  work  will  not  permit  going  too  much  into  the 
details  of  machine  tool  construction.  It  is,  however,  hoped  that 
the  principal  points  of  construction  and  methods  of  operation  may 
be  brought  out  clearly  and  in  such  a  way  as  to  aid  the  young 
mechanic  in  quickly  becoming  master  of  the  several  classes  of 
machine  tool  operations  above  enumerated,  and  suggest  some 
thought  for  the  older  mechanic. 


CONTENTS. 


CHAPTER  I. 
The  Hammer  and  Cold  Chisel 17  to    21 

CHAPTER  II. 
The  File  and  Filing 22  to    47 

CHAPTER  III. 
Scrapers  and  Scraped   Surfaces 48  to    54 

CHAPTER  IV. 
Standards  of  Measure 55  to    63 

CHAPTER  V. 
Calipers     64  to    81 

CHAPTER  VI. 
Gauges    and    Indicators 82  to    92 

CHAPTER  VII. 
Rules,  Squares  and  Other  Small  Tools 93  to  102 

CHAPTER  VIII. 
Drills    103  to  113 

CHAPTER  IX. 
Reamers     114  to  124 

CHAPTER  X. 
Taps  and   Dies 125  to  141 

CHAPTER  XI. 
Drill  and   Tap  Holders 142  to  153 

CHAPTER  XII. 
Mandrels 154  to  162 

CHAPTER  XIII. 
The    Lathe 163  to  181 

CHAPTER  XIV. 
The  Lathe  in  Modified  Forms 182  to  196 

CHAPTER  XV. 
Lathe    Tools 107  to  209 

CHAPTER  XVI. 
Chucks  and  Drivers  for  Lathe  Work 210  to  219 


l6  CONTENTS. 

CHAPTER  XVII. 
Lathe  Work,  Between  Centers 220  to  247 

CHAPTER  XVIII. 
Lathe  Work  on  Face  Plate,  Chuck  and  Carriage 248  to  263 

CHAPTER  XIX. 
Boring  and  Turning  Mills 264  to  272 

CHAPTER  XX. 
Planing  and  Shaping  Machines,  Their  Tools  and  Attachments     273  to  298 

CHAPTER  XXI. 
Planer   and   Shaper   Work 299  to  305 

CHAPTER  XXII. 
The  Slotting  Machine  and  Key  Seater 306  to  311 

CHAPTER  XXIII. 
Milling    Machines 312  to  335 

CHAPTER  XXIV. 
Milling   Machine    Cutters 336  to  349 

CHAPTER  XXV. 
Milling  Machine  Work 350  to  378 

CHAPTER  XXVI. 
Gear  Cutters  and  Gear  Cutting 379  to  396 

CHAPTER  XXVII. 
Drilling  Machines  and  Drilling  Work 397  to  422 

CHAPTER  XXVIII. 
Grinding  Machines  and  Grinding 423  to  439 

CHAPTER  XXIX. 
Hardening  and  Tempering 440  to  449 

CHAPTER  XXX. 
Fastenings     ; 450  to  462 

CHAPTER  XXXI. 
Gearing    463  to  489 

CHAPTER  XXXII. 
Belting   and    Transmission    Machinery 49010516 

CHAPTER  XXXIII. 
Miscellaneous  Shop  Equipment  and  Conveniences 517  to  527 

CHAPTER  XXXIV. 
Useful  Tables  and  Data 528  to  544 


OF  THE        ^A 

UMiVZRSITY 


CHAPTER  I. 

THE  HAMMER  AND  COLD  CHISEL. 

The  hammer  and  cold  chisel  are  a  noisy  pair  with  which  the 
apprentice  becomes  acquainted  early  in  his  shop  experience,  and 
his  aching  arms  and  battered  knuckles  tell  of  the  introduction. 

The  machinist  hammer,  as  generally  used,  weighs  from  three- 
fourths  to  one  and  one-half  pounds,  exclusive  of  handle.  It 


FIG.  r. 


is  made  of  high-grade  steel,  carefully  tempered  on  head  and 
pene  and  usually  of  the  form  shown  in  Fig.  i.  The  eye  is  left 
soft  as  it  will,  in  that  condition,  better  resist  the  shock  without 
danger  of  cracking.  The  head  is  usually  made  cylindrical  with 


FIG.  2. 


a  slightly  crowning  face.  For  the  ball  pene  is  often  substituted 
the  straight  pene,  Fig.  2,  and  the  cross  pene,  Fig.  3.  The  pene 
is  used  almost  entirely  for  riveting  purposes.  The  eye  should 


l8  MODERN    MACHINE    SHOP    TOOLS. 

be  enlarged  slightly  at  each  end ;  the  handle  can  then  be  fitted 
in  from  one  side  and  wedged  to  fill  the  enlargement  of  the  eye 
on  the  other  side.  Hard,  smooth  wedges  are  not  suitable  for  this 
purpose,  as  they  jar  loose  too  easily.  Soft  wood  or  roughed  metal 
wedges  serve  the  purpose  well. 

The  handle  should  be  of  straight-grained,  dry,  second-growth 
hickory,  twelve  to  sixteen  inches  long;  depending  on  the  weight 
of  the  hammer.  The  handle  should  not  be  too  stiff  in  the  shank, 
as  too  rigid  a  connection  between  hammer  and  hand  causes  undue 
shock,  and  consequent  tiring  of  the  hand.  It  should  be  so  set  in 
the  eye  that  its  length  is  at  right  angles  to  the  axis  of  hammer 
head,  and  its  long  cross  section  parallel  with  this  axis. 

The  face  of  the  hammer  should  be  kept  true  and  smooth,  by 
careful  grinding  and  polishing.  Should  the  edges  become  chipped 


FIG.  3. 

a  good  smith  can  dress  and  retemper  the  head,  making  it  as  good 
as  new. 

In  its  use  the  hammer  should  be  grasped  near  the  end  of  the 
handle,  giving  it  a  free  arm  swing  and  carrying  the  head  through 
a  nearly  vertical  plane.  If  the  plane  of  the  swing  approaches  a 
horizontal  the  weight  of  the  hammer  will  produce  a  twisting 
effort  on  the  fore  arm  which  will  be  very  wearing.  The  handle 
should  be  grasped  with  only  sufficient  force  to  safely  control  the 
blow. 

Machinists'  cold  chisels,  for  ordinary  shop  uses,  are  generally 
made  from  seven-eighths  or  three-fourths  inch  octagonal  steel, 
and  when  new  should  be  about  eight  inches  long.  The  flat  sur- 
facing chisel,  as  shown  in  Fig.  4,  should  be  dressed  about  three 
inches  back  from  the  cutting  edge.  The  flats  A  A  should  be 
plane  surfaces  symmetrical  with  the  sides  of  the  octagon.  The 


THE    HAMMER    AND    COLD    CHISEL.  1C) 

thickness  of  the  bit  at  C  should  not  exceed  three-sixteenths  inch 
for  ordinary  work  and  can  usually  be  made  somewhat  thinner. 
Care  must  be  exercised  in  the  grinding  of  the  facets  c  c.  The 
angle  of  their  faces  with  each  other  will  depend  on  the  hardness 
of  the  metal  to  be  cut.  For  the  softer  metals,  as  copper,  babbitt 
and  lead,  25  degrees  to  30  degrees  will  work  well;  for  brass  and 


FIG.  4. 


FIG.   5. 


cast  iron,  40  degrees  to  55  degrees ;  and  for  steel,  60  degrees  to 
70  degrees.  The  smaller  this  angle  the  more  nearly  will  the  center 
line  of  the  chisel  approach  the  plane  of  the  work  and  the  greater 
will  be  the  cutting  resultant  of  the  blow.  It  is  therefore  advisable 
to  make  this  angle  as  small  as  the  nature  of  the  work  will  permit. 
These  facets  should  be  ground  straight  in  their  width,  as  shown 
at  A,  Fig.  5  :  not  rounded  as  shown  at  B,  as  in  that  case  the 
facet  would  not  form  a  guide  and  it  would  be  found  difficult  to 


FIG.  6. 


FIG.  7. 


make  a  smooth,  straight  cut.  The  facets  should  also  be  ground 
at  a  uniform  angle  with  the  flats,  thus  bringing  the  cutting  edge 
parallel  with  the  flats,  as  shown  in  end  view  at  A,  Fig.  6,  and 
not  as  shown  at  B.  The  cutting-edge  formed  by  the  intersection 
of  these  facets  should  be  at  right  angles  to  the  length  of  the  chisel. 
For  smooth  chipping  the  cutting-edge  should  be  slightly  rounded 
in  its  length,  as  shown  in  Fig.  7.  When  ground  straight  the  cor- 
ners, e  e,  are  likely  to  dig  into  the  work  and  are  more  apt  to  break 
away  than  when  ground  rounding. 


2O 


MODERN    MACHINE    SHOP    TOOLS. 


In  forging,  the  cutting-edge  should  always  be  made  wider 
than  the  diameter  of  the  body  of  the  chisel.  When  the  tool  is  to 
be  used  on  wrought  iron  or  steel  this  width  should  exceed  the 
diameter  from  one-thirty-second  to  one-sixteenth  of  an  inch, 
Fig.  4;  but  when  for  use  on  the  softer  metals  the  excess  may 
be  as  much  as  one-half  of  the  diameter  of  the  body,  as  shown  in 
Fig.  12. 

The  flat  chisel  can  be  modified  in  form  to  suit  special  con- 
ditions, as  for  example,  the  cutting  of  the  flat  sides  of  a  mortise 
requires  a  chisel  the  axis  of  which  will  follow  a  line  nearly  par- 
allel to  the  work  surface.  Such  a  chisel  is  shown  in  Fig.  8,  in 


FIG.  8. 

which  one  flat  is  parallel  with  the  length  of  chisel  having  at  the 
end  a  wide  facet  at  a  slight  angle  with  the  length,  this  in  order 
to  be  able  to  guide  and  control  the  cutting-edge  of  the  tool. 

The  cape  chisel  is  used  as  a  parting  tool,  for  grooving  and  key 
waying.     It  is  of  the  general  form  shown  in   Fig.  9.     In  this. 


FIG.  9. 

chisel  the  thickness  at  A  must  be  less  than  the  length  of  the 
cutting-edge  in  order  that  the  tool  can  be  given  a  small  amount  of 
side-motion  in  the  groove  it  cuts,  otherwise  it  would  be  difficult 
to  guide  the  cutting-edge.  This  chisel,  when  made  as  shown  in 
Fig.  10,  forms  the  tool  usually  used  for  grooving  straight  oil  ways. 


FIG.    10. 


THE    HAMMER    AND    COLD    CHISEL. 


21 


in  loose  pulleys  and  shaft-bearings.  For  cutting  spiral  grooves  in 
half  boxes  this  chisel  should  be  forged  with  a  curved  instead  of  a 
straight  bottom  face. 

The  diamond-pointed  chisel  is  shown  in  Fig.  n.    This  tool  is 


FIG.  II. 

usually  used  for  squaring  corners,  and  is  generally  made  as  shown 
in  figure. 

The  head  of  all  chisels  should  be  dressed  round  and  somewhat 
reduced  in  diameter,  as  shown  in  figures.  When  the  head  be- 
comes battered  redress  it,  as  small  pieces  of  steel  are  apt  to  fly 
from  a  bushed  chisel  head,  embedding  themselves  deeply  in  the 
hand  holding  the  chisel. 

In  using  the  cold  chisel  grasp  it  near  the  head  with  the  full 
hand,  knuckles  up.  Do  not  hold  it  too  tightly  but  with  sufficient 
force  only  to  guide  and  hold  it  to  the  work.  When  the  surface 
of  the  work  is  difficult  to  get  at  the  workman  is  justified  in  hold- 
ing the  chisel  between  thumb  and  fingers,  or  with  palm  of 
hand  up. 

The  eye  should  follow  the  cutting-edge,  not  the  head  of  the 
chisel,  when  delivering  the  blow,  and  light  taps  with  the  hammer 
should  not  be  used  before  each  heavy  blow.  It  will  require 


FIG.  12. 


some  practice  before  the  beginner  can  accomplish  this    .  ithout 
disastrous  results  to  his  knuckles. 

In  tempering  the  chisel  for  general  machine  shop  work  it 
should  be  drawn  nearly  to  a  blue  which  gives  a  tough  temper  that 
will  stand  well  on  all,  except  chilled  iron  and  hard  steel  work. 


CHAPTER    II. 

THE    FILE    AND    FILING. 

A  piece  of  high-grade  crucible  steel,  forged  to  shape,  ground, 
cut  and  carefully  tempered,  forms  that  tool  so  indispensable  to 
the  mechanic — the  file. 

The  file  maker  is  no  longer  compelled  to  forge  his  blanks  from 
stock  of  unsuitable  proportion,  but  receives  from  the  steel  manu- 
facturers stock  of  the  required  cross-section  to  make  all  standard 
shapes.  This  reduces  the  forging  to  a  minimum,  it  being  only 
necessary  to  cut  the  stock  to  the  required  lengths,  to  draw  down 
the  point  and  form  the  tang,  the  latter  operations  being  very 
rapidly'  performed  under  power  hammers. 

The  National  Association  of  File  Manufacturers  prescribe  to 


1 


i-i 


16" 


FIG.   13. 


the  steel  makers  the  forms  of  cross-sections  they  require.  Con- 
sequently, all  makers  of  file  steel  can  furnish  any  section  correct 
to  gauge.  In  Fig.  13  are  shown  the  correct  cross-sections  of 
steel  for  flat  files,  even  inch  lengths,  from  4  to  16  inches.  In 
Fig.  14  are  shown  the  cross-sections  of  file  steel  for  all  the  shapes 
in  general  use.  Each  section  is  for  an  8-inch  file,  full  scale.  The 
names  of  the  files  made  from  steel  of  these  sections  are,  referring 
to  the  numbers  of  the  figure:  I,  "Hand";  2.,  "Flat";  3,  "Mill";  4, 
"Pillar";  5,  "Warding";  6,  "Square";  7,  "Round";  8,  "Half- 
round";  9,  "Three-square";  10,  "Knife";  n,  "Pit-saw";  12, 
"Crossing";  13,  "Tumbler";  14,  "Cross-cut";  15,  "Feather-edge"; 
16,  "Cant-saw";  17,  "Cant-file";  18,  "Cabinet";  19,  "Shoe-rasp"; 
20,  "Rasp." 


THE    FILE   AND    FILING.  23 

It  will  be  noticed  that  many  of  these  files  are  named  from  the 
form  of  their  cross-section,  and  that  those  so  named  are  the 
ones  most  used  for  general  work;  while  the  others  receive  their 
names  from  the  special  character  of  the  work  they  are  expected  to 
be  used  upon.  It  will  also  be  noted  that  the  stock  for  files  of  rec- 
tangular cross-section  may  be  classified  as  to  thickness  as  fol- 
lows: "Square,"  the  thickest;  "Pillar,"  "Hand,"  "Flat,"  "Rasp" 
and  "Warding."  As  to  width,  "Hand"  is  the  widest;  "Flat," 
"Rasp,"  "Mill"  and  "Warding"  are  the  same  width;  "Pillar" 
materially  narrower,  and  "Square"  the  narrowest. 

The  "Half-round"  is  not  a  full  semicircle,  the  arc  being  about 


one-third  of  the  full  circle.  On  the  other  hand,  the  "Pit-saw"  is 
a  full  half  circle  in  section. 

The  "Three-square,"  "Cant-saw"  and  "Cant-file"  differ  in  sec- 
tion in  their  angles,  the  former  having  equal  angles,  60  degrees, 
and  equal  sides,  the  next  35 — 35  and  no-degree  angles,  and  the 
latter  30 — 30  and  i2O-degree  angles. 

The  length  of  the  file  is  measured  from  point  to  heel,  and  does 
not  include  the  tang.  The  tang  is  usually  made  spike  shaped  to 
receive  a  plain  ferrule  handle.  Some  makers  modify  the  form 
of  tang  to  fit  patented  handles. 

As  forged,  the  blank  for  a  "Hand"  file,  Fig.  15,  is  parallel  in 


24  MODERN    MACHINE    SHOP    TOOLS. 

thickness  from  heel  to  middle  and  tapered  from  middle  to  point, 
making  the  point  about  one-half  the  thickness  of  the  stock.  The 
edges  of  the  blank  are  usually  left  parallel.  They  are,  however, 
sometimes  drawn  in  slightly  at  the  point. 

The  "Flat"  file  blank,  Fig.  16,  is  parallel  in  both  of  its  longi- 
tudinal sections  from  heel  to  middle  and  tapered  in  both  sections 
from  middle  to  point,  the  thickness  of  point  being  about  two- 
thirds,  and  width  about  one-half  that  of  the  stock. 

For  the  "Mill"  file  the  blank  is  parallel  in  thickness  from  heel 
to  point,  and  usually  tapered  to  about  three-fourths  the  width 


FIG.  15. 


FIG.   l6. 


of  the  stock.  The  "Mill"  file  is  often  made  blunt— that  is,  of 
equal  width  and  thickness  throughout  its  length. 

The  blank  for  the  "Warding"  file  is  tapered  in  width  from 
heel  to  point  and  is  of  uniform  thickness.  Aside  from  width,  the 
"Pillar"  file  is  similar  to  the  "Hand"  file.  The  "Pillar"  file  is  also 
made  in  narrow  and  extra  narrow  patterns,  the  extra  narrow 
approximating  a  square  in  section. 

The  "Three-square,"  "Square"  and  "Round"  are  also  made  in 
slim  and  blunt  forms.  The  "Slim"  is  a  file  of  regular  length,  but 
smaller  cross-section,  and  the  "Blunt"  of  equal  cross-section 
from  heel  to  point,  being  either  "slim"  or  regular. 

After  forging,  the  blanks  are  thoroughly  annealed  in  annealing 


THE    FILE    AND    FILING.  25 

furnaces,  the  operation  taking  from  twenty-four  to  thirty-six 
hours.  When  the  blank  comes  from  the  furnace,  it  is  twisted 
and  scaly,  and  must  be  subjected  to  a  straightening  process, 
after  which  the  scale  is  removed  by  grinding  on  very  heavy 
grind-stones.  The  blanks  are  next  draw-filed  to  make  them 
perfectly  smooth  and  even,  after  which  they  are  ready  for  the 
cutting. 

Files  are  classified  under  three  heads — "Single-cut,"  "Double- 
cut"  and  "Rasp."  The  "Single-cut"  file — or  "Float,"  as  its  coarser 
cuts  are  sometimes  called — has  surfaces  covered  with  teeth  made 
by  single  rows  of  parallel  chisel  cuts  extending  across  the  faces 
at  an  angle  of  from  65  to  85  degrees  with  the  length  of  the  file. 
The  size  of  this  angle  depends  on  the  form  of  the  file  and  the 
nature  of  the  work  it  is  to  perform. 

The  "Double-cut"  file  has  two  rows  of  chisel  cuts  crossing 
each  other.  The  first  row  is,  for  general  work,  at  an  angle  with 


FIG.  17. 

the  length  of  the  file  of  from  40  to  45  degrees,  and  the  second 
row  from  70  to  80  degrees.  In  the  "Double-cut"  finishing  files 
the  angle  of  the  first  cut  is  about  30  degrees,  and  the  second  from 
80  to  87  degrees  with  the  axis  of  the  file.  The  "Double-cut"  gives 
a  broken  tooth,  the  surface  of  the  file  being  made  up  of  a  large 
number  of  small,  oval-pointed  teeth  inclined  toward  the  point, 
and  resembling  in  shape  the  cutting  end  of  a  diamond  pointed 
cold  chisel. 

In  the  rasp  the  teeth  are  entirely  disconnected  from  each  other. 
They  are  round  on  top,  and  are  formed  by  raising,  with  a  punch, 
small  portions  of  stock  from  the  surface  of  the  blank.  The  ma- 
chinist seldom  has  use  for  a  rasp,  as  they  are  intended  for  filing 
the  softer  materials,  as  wood  and  leather. 

The  regular  grades  of  cut  upon  which  the  coarseness  of  a 
file  depends  are  "Rough,"  "Coarse,"  "Bastard,"  "Second-cut," 
"Smooth"  and  "Dead-smooth."  The  "Rough"  file  is  usually 


26 


MODERN    MACHINE    SHOP    TOOLS. 


single  cut  and  the  "Dead-smooth"  double  cut.  The  other  grades 
are  made  in  both  double  and  single  cut.  These  grades  of  coarse- 
ness are,  however,  only  comparable  when  files  of  the  same  length 
are  considered,  as  the  longer  the  file  in  any  cut,  the  fewer  the 
teeth  per  inch  of  length.  This  is  shown  in  Fig.  17,  where  a  4- 
inch  and  1 2-inch  "Bastard"  file  are  placed  side  by  side  for  com- 
parison. 

The  relative  degrees  -of  coarseness  for  the  different  cuts  are 


COARSE.  BASTARD.  SECOND   CUT.  SMOOTH. 

FIG.     l8. 

shown,  for  the  "Single-cut"  in  Fig,  18,  and  the  "Double-cut"  in 
Fig.  19,  a  portion  of  an  8-inch  file  being  taken  in  each  case. 

The  value  of  a  file  depends  entirely  upon  three  things — quality 
of  stock  from  which  it  is  made,  the  form  of  its  teeth  and  the 
temper.  The  stock  should  be  of  the  very  best,  as  tool  steel  is 
seldom  put  to  any  use  where  its  lasting  qualities  are  more  severely 
taxed. 

As  to  the  forming  of  the  teeth :   It  is  only  within  the  past  few 


COARSE.  BASTARD.  SECOND   CUT.  SMOOTH. 

FIG.   19. 

years  that  machine-cut  files  have  come  prominently  upon  the 
market,  it  being  generally  believed  that  a  file  to  be  first  class 
must  be  hand  cut.  In  Fig.  20  are  shown  portions  of  two  1 4-inch 
flat  "Bastard"  files;  of  these  one  is  hand  and  one  machine  cut. 
The  difference  between  these  cuts  is  so  slight  that  only  an  expert* 


THE    FILE    AND    FIUXC,. 


with  the  files  rather  than  their  pictures  before  him,  could  tell, 
with  any  degree  of  certainty,  which  was  the  hand  and  which  the 
machine  cut. 

Up  to  the  time  of  the  perfecting  of  the  increment  cut  file,  the 
great  trouble  with  machine-cut  files  was  in  the  perfect  uniformity 
of  the  teeth.  In  a  hand-cut  file  the  width  and  spacing  of  the 
teeth  depend  entirely  upon  the  skill  of  the  workman  ;  and  no 
matter  how  carefully  he  does  the  cutting,  irregularities  of  a 
thousandth  of  an  inch,  more  or  less,  will  occur  in  the  spacing 
and  in  the  angle  at  which  he  holds  the  broad  chisel  that  forms 
the  teeth.  These  slight  variations  will  cause  the  teeth  to  be  of 
uneven  height  and  irregular  outline.  These  irregularities  are 
now  very  faithfully  reproduced  in  the  increment,  machine-cut 
file. 

It  is  difficult  to  make  a  file  having  teeth  of  uniform  height  and 


FIG.  2O. 

outline,  as  in  the  case  of  the  ordinary  machine-cut  file,  take 
hold  of  the  work.  The  reason  for  this  is  that  so  many  teeth 
present  themselves  to  the  work  surface  that  the  workman  must 
exert  great  pressure  on  the  file  to  make  them  bite.  With  the 
file  having  teeth  of  irregular  height,  fewer  will  come  in  contact 
with  the  work,  and  the  pressure  required  to  make  them  take  hold 
will  be  correspondingly  light.  As  these  long  teeth  wear  down, 
the  shorter  ones  will  begin  to  do  work ;  but  the  file  will,  of  course, 
not  cut  so  freely  as  when  new.  Again,  in  using  the  file  with 
teeth  of  uniform  height,  it  will,  when  pushed  to  the  work,  pro- 
duce, at  the  start,  grooves  which  will  grow  deeper  as  the  file  is 
moved  forward,  and,  due  to  the  broad  cut,  will  be  quite  certain  to 
vibrate  and  "chatter."  On  the  other  hand,  the  uneven  teeth  of 
the  hand  and  increment  cut  files,  will  so  adapt  themselves  to  the 


28  MODERN    MACHINE    SHOP    TOOLS. 

surface  of  the  work  that  only  a  few  teeth  at  any  particular  point 
in  the  length  of  the  file  will  cut.     The  metal  left  between  these 
teeth  will  be  removed  by  the  teeth  following,  perhaps  a  dozen  or 
more  rows  of  teeth  being  required  to  finish  the  cut  started  by 
one.     This  is  shown,  for  a  "Single-cut"  file,  in  Fig.  21,  where 
the    several    irregular    lines    represent    as 
many  tooth  outlines  drawn  on  an  exagger- 
ated scale.     These  teeth  come  successively 
HHHm  to  the  work,   and  if   all   their   high  points 

were  brought  together  they  would  form  a 
straight  line,  as  shown,  which  would  be  the 
outline  of  the  resulting  cut. 

The  cutting  of  an  increment  cut  file  con- 
sists in  the  forming  of  the  teeth  by  a  chisel 
operated  in  a  machine,  and  so  controlled 

that  the  spacing  between  teeth  may  be  increased  or  decreased,  the 
same  being  subject  to  a  small  amount  of  irregularity,  as  well  as 
a  slight  variation  in  the  angle  of  the  teeth  with  each  other.  As 
manufactured  by  one  company,  the  spacing  of  the  teeth  from 
point  to  middle  is  increased,  and  from  middle  to  heel  decreased. 
Another  leading  manufacturer  increases  the  pitch  from  point  to 
heel.  It  will  be  understood  that  the  increment  of  space  is  very 
small.  In  a  12-inch  "Bastard"  file,  having  teeth  spaced  progres- 
sively wider  from  point  to  heel,  the  pitch  of  teeth  at  heel  is  about 
.01  of  an  inch  greater  than  at  the  point,  which  makes  the  average 
increase  per  tooth  about  .00003  °f  an  mcn- 

In  machine-made  files  the  cutting  is  very  rapidly  performed, 
the  chisel  receiving  from  500  to  3,500  blows  per  minute,  de- 
pending on  the  weight  of  the  file  being  cut.  The  blank  is  cut 
from  point  to  heel,  and  when  turned  over  is  placed  on  lead  strips 
to  protect  the  teeth  already  formed. 

After  cutting,  the  files  are  inspected  and  assorted  as  to  quality. 
They  are  then  tempered,  any  material  change  in  shape  due  to 
hardening  being  lectified  at  the  time  of  tempering,  after  which 
they  are  ready  for  final  inspection.  This  consists  of  trying  each 
file  on  a  piece  of  hard  steel  and  making  sure  that  it  is  free  from 
temper  cracks.  They  are  next  coated  with  oil  and  wrapped  in 
oiled  paper,  to  prevent  rusting,  after  which  they  are  packed  in 
boxes,  ready  for  the  market. 

The  teeth  of  a  file  remove  metal  by  a  shearing  cut.  This  is 
most  apparent  in  the  "Single-cut"  files,  where  the  teeth  have 


THE    FILE    AND    FILING.  29 

lateral  length;  but  is  equally  true  of  the  pointed  tooth  of  the 
"Double-cut"  file. 

A  file  bites  freer  on  work  having  a  narrow  surface  than  a  wide, 
because  fewer  teeth  come  in  contact,  at  any  point  in  the  stroke, 
with  the  work  surface,  and  consequently  less  pressure  is  required 
to  make  the  file  bite.  On  very  thin  work  the  teeth  of  a  "Double- 
cut"  file  bite  so  freely  that  the  danger  of  breaking  them  is  great. 
For  work  of  this  character  the  long  tooth  of  the  "Single-cut"  is 
best  adapted,  as  its  form  gives  it  greater  strength,  and  the  shear 
of  the  cut  is  smoother,  one  tooth  coming  into  cut  as  another 
leaves.  On  the  broad  surfaces,  however,  the  teeth  of  the  "Double- 
cut"  have  the  advantage. 

A  file  is  "tapered"  when  it  is  thinner  at  the  point  than  at  the 
middle,  and  is  "full  tapered"  when  thinner  at  point  and  heel  than 
at  the  middle.  The  reasons  for  thus  tapering  a  file  are,  first  to 


FIG.  22. 


reduce  the  number  of  teeth  that  come  in  contact  with  the  work, 
and,  second,  to  enable  the  operator  to  file  a  straight  or  plane 
surface.  The  first  reason  is  evident ;  the  second  is  shown  in  Fig. 
22.  If  the  file  is  perfectly  straight,  as  shown  in  i,  the  motion 
in  order  to  produce  a  plane  surface  on  the  work  must  be  abso- 
lutely parallel  to  this  surface.  This  the  most  expert  mechanic 
can  scarcely  be  expected  to  do,  and  the  result  will  be  work 
rounded  at  the  edges  A  and  B.  If  the  file  is  tapered,  its  surface 
will  be  slightly  convex,  as  shown  in  2,  and  if  moved  entirely 
across  the  surface,  straight  work  will  result.  The  workman  will 
experience  little  difficulty  in  accomplishing  this,  as  he  can  allow 
the  motion  of  the  file  to  deviate  slightly  from  a  straight  line,  and 
stnr  not  cut  away  the  edges  A  and  B.  If  the  file  is  not  moved 
clear  across  the  work,  a  concave  surface  will  of  course  result. 


3O  MODERN    MACHINE    SHOP    TOOLS. 

The  tempering  is  certain  to  distort  the  file  somewhat,  and  it 
will,  as  a  result,  usually  be  found  to  have  more  "belly,"  as  this 
convex  quality  is  called,  on  one  side  than  on  the  other.  It  is 
the  side  having  the  most  "belly,"  and  the  highest  part  of  that, 
that  the  careful  mechanic  will  always  select  for  use  in  his  most 
particular  work.  This  high  point  he  readily  finds  by  running 
his  eye  along  the  edge  of  the  file  from  point  to  heel. 

The  file  does  not  bite  the  cast  metals  as  readily  as  it  does  the 
rolled,  consequently  a  sharper  file  is  required  for  cast  iron  and 
brass  than  for  wrought  iron  and  steel.  For  these  reasons  the 
new  files  should  be  first  used  on  the  cast  iron  and  brass,  and  when 
they  become  too  dull  to  work  these  metals  efficiently,  they  may 
be  used  on  the  steel  and  wrought  work.  A  new  file  will  pin  and 
tear  the  surface  of  these  latter  metals  much  worse  than  the  file 
that  has  seen  a  moderate  amount  of  duty  on  cast  iron  and  brass. 
A  new  file  will  leave  a  smoother  surface  after  it  has  been  used 
for  a  few  strokes,  these  strokes  causing  the  high  teeth  to  give 
down  a  little,  which  prevents  the  danger  of  their  scratching  the 
work. 

The  first  dozen  strokes  of  a  new  file  on  a  tough  piece  of  steel 
frequently  lessens  its  cutting  value  as  much  as  an  hour's  steady 
use  on  soft  cast  iron,  yet  not  seriously  injuring  it  for  the  steel 
work.  Narrow  surfaces  are  exceedingly  hard  on  new  files,  and 
especially  so  on  the  double  cuts,  as  but  few  teeth  come  in 
contact  with  the  work,  and  they  bite  so  freely  that  they  are  broken 
off  by  the  excessive  strain. 

Not  until  the  file  becomes  too  dull  to  be  used  efficiently  on  the 
narrow  steel  work  should  it  be  used  on  the  scale  of  cast  iron  or 
forgings,  as  this  scale  is  frequently  harder  than  the  file. 

The  term  "cross-filing"  applies  to  those  filing  operations  in 
which  the  file  is  pushed  endwise  across  the  work.  When  in  cross- 
filing  the  character  of  the  work  requires  a  heavy  file,  it  should 
be  held  in  both  hands,  as  shown  in  Fig.  23,  the  end  of  the  handle 
abutting  against  the  palm  of  the  hand,  thus  giving  a  good  bear- 
ing to  receive  the  thrust  on  the  work  stroke.  When  held  in  this 
manner  an  extremely  tight  grip  is  not  required,  which  makes  it 
much  easier  on  the  fingers  and  enables  the  workman  to  more  read- 
ily control  the  file. 

When  a  very  light  file  is  being  used  on  the  work  it  is  usually 
best  to  hold  it  with  one  hand,  as  shown  in  Fig.  24.  In  this  case  the 
thumb  rests  against  the  side  of  the  file  just  ahead  of  the  handle, 


THE    FILE    AND    FILING. 


and  the  fore  finger  extends  along  the  top,  considerable  downward 
pressure  being  exerted  by  this  finger,  as  near  as  possible,  over 
the  working  surface  of  the  tool. 

When  the  file  is  of  medium  size  and  thin,  if  held  as  shown  in 
Fig.  23,  the  pressure  at  the  ends  will  bend  it  down,  making 


FIG.  23. 


FIG.  24. 


FIG.  25. 


FIG.  26. 


it  concave  on  its  under  surface,  which  will  cause  it  to  cut 
away  the  metal  at  the  edges,  as  shown  in  Fig.  25.  If,  however,  it 
is  held  as  shown  in  Fig.  26,  the  downward  pressure  of  the  thumb 
will  spring  the  file  in  the  opposite  direction,  and  thus  enable  the 


32  MODERN    MACHINE    SHOP   TOOLS. 

operator  to  move  it  across  the  work  without  cutting  away  the 
edges.  When  the  thumb  becomes  tired,  the  position  shown  in 
Fig.  23  can  again  be  taken,  the  ball  of  the  thumb  bearing  down 
hard  on  the  file  and  the  fingers  lifting  at  the  point  accomplish 
the  same  object.  Either  of  these  methods  of  holding  is  difficult 
to  maintain  for  more  than  a  few  moments  at  a  time,  consequently 
a  stiffer  file,  having  considerable  belly,  is  preferable  on  work  of 
this  character. 

The  value  of  a  good  file  handle  should  be  appreciated.  It 
should  be  of  good  size,  well  formed,  smooth,  properly  ferruled 
and,  most  important  of  all,  so  secured  to  the  tang  that  its  cen- 
ter line  is  parallel  with  the  length  of  the  file.  Handles  made  of 
soft,  tough  wood  are  preferable,  as  they  are  lighter  and  less  liable 
to  crack  when  forced  on  the  tang.  The  soft-wood  handle,  if  pro- 
vided with  a  hole  for  the  reception  of  the  tang  of  a  diameter 
slightly  greater  than  the  thickness  of  the  tang,  can  be  driven  on 
without  danger  of  cracking.  If  of  hard  wood  a  good  job  requires 
heating  the  tang  red  hot  and  burning  the  hole  in  the  handle  to 
fit  it.  Care  must  be  exercised,  or  the  temper  of  the  teeth  near 
the  heel  will  be  drawn.  A  piece  of  wet  waste  wrapped  around  the 
heel  will  prevent  this. 

When  the  work  surface  is  so  broad  that  the  file  cannot  be  held, 
as  shown  in  Fig.  23,  on  account  of  the  handle  striking  against 
the  edge  of  the  work,  a  surface  file  holder  must  be  used.  In 
Fig.  27  is  shown  such  a  holder.  The  bottom  of  the  handle  is  pro- 


FIG.  27. 

vided  with  a  tapered,  dove-tail  slot  to  receive  the  tang,  the  outer 
point  resting  on  the  top  of  the  file.  Before  applying  the  handle 
file  the  edges  of  the  tang  to  approximately  fit  the  dove-tail  slot, 
as  this  may  save  a  jammed  set  of  knuckles.  In  using  a  file  with 
this  holder,  the  fingers  of  the  left  hand,  resting  on  the  top  of  the 
file,  must  give  nearly  all  the  pressure  necessary  to  make  it  cut. 

The  form  of  surface  file  holder  shown  in  Fig.  28  possesses  the 
advantage  of  giving  the  operator  a  handle  similar  in  shape  and 
position  to  that  used  on  ordinary  narrow  work.  The  rod  en-. 


THE    FILE    AND    FILINC. 


33 


ables  the  left  hand  to  so  grasp  the  point  of  the  file  that  the  down- 
ward pressure  may  be  applied  with  less  fatigue  to  the  hand  than 
in  the  case  shown  in  Fig.  27.  When  the  handle  is  screwed  tight 
against  the  shoulder,  the  rod  draws  up  on  the  point,  thus  tending 
to  give  the  file  more  curvature,  an  advantage  of  considerable  mo- 
ment in  filing  accurate  plane  surfaces. 

Ordinarily  the  surface  of  the  work  on  which  the  file  is  to  be 
used  should  be  held  at  the  height  of  the  workman's  elbow,  thus 
allowing  the  direction  of  motion  of  his  forearm  to  be  in  a  line 
parallel  with  the  plane  of  the  work  surface.  This  position  of  the 
work  allows  the  workman's  arm  to  swing  freely  at  the  shoulder 
with  the  least  possible  amount  of  motion  at  the  wrrist  and  elbow. 
If  the  work  surface  is  broad  it  should  be  held  somewhat  lower 
than  the  elbow,  thus  enabling  the  workman  to  more  easily 
reach  over  the  entire  surface.  If,  on  the  other  hand,  the  work 
is  of  a  fine  character,  depending  largely  on  the  eyes  and  a  delicate 
touch,  it  should  be  held  much  higher.  For  work  of  this  char- 
acter the  file  is  usually  held  in  one  hand  and  the  high  position  of 


the  work  prevents  the  fatigue  incident  to  a  bent  position  over  fine 
work. 

For  heavy  cross-filing,  which  requires  a  considerable  amount 
of  pressure  on  the  file,  the  workman  should  stand  slightly  back 
from  the  work  with  one  foot  considerably  in  advance  of  the 
other.  On  the  forward,  or  work  stroke,  the  pressure  exerted 
on  the  file  should  relieve  the  weight  on  the  forward  foot,  the 
rear  foot  bracing  against  the  stroke.  On  the  return  stroke  the 
forward  foot  should  again  take  its  portion  of  the  weight,  and 
the  file  should  be  relieved  from  all  pressure,  but  not  raised  from 
the  surface  of  the  work.  Only  at  such  times  as  it  is  necessary 
to  examine  the  condition  of  the  surface  being  operated  upon 
should  the  file  be  taken  from  the  work,  its  removal  for  cleaning, 
however,  being  excepted. 

The  workman's  body  should,  in  heavy  cross-filing,  move  back 
and  forward  with  the  strokes,  thus  making  the  back  and  legs 
do  a  part  of  the  work  that  would  otherwise  come  entirely  on  the 


34  MODERN    MACHINE    SHOP    TOOLS. 

arms.  When  the  work  is  of  a  lighter  character  and  the  quality 
of  the  finished  surface  rather  than  the  quantity  of  metal  removed 
must  be  considered,  the  workman  should  stand  in  an  upright 
position,  doing  most  of  the  work  with  his  arms. 

In  cross-filing,  and  more  especially  where  much  metal  is  to  be 
removed,  the  direction  of  the  strokes  should  be  varied  fre- 
quently. This  not  only  enables  the  production  of  truer  work, 
but  faster  reduction  of  the  metal.  The  file  when  pushed  end- 
wise produces  small  grooves  or  channels  in  the  direction  of  the 
stroke,  and  when  the  direction  of  the  stroke  is  changed  the  file 
teeth  com'e  in  contact  with  the  tops  of  the  ridges  between  the 
grooves,  thus  diminishing  the  area  of  tooth  contact  with  the 
work  surface,  and  consequently  increasing  the  bite;  that  is,  for 
equal  pressures. 

In  cross-filing  the  file  should  be  held  at  quite  an  angle  with 
the  direction  of  the  stroke,  which  has  the  effect  of  giving  the 
file  a  side  motion  as  it  is  swept  forward.  This  improves  the 


FIG.  29. 

condition  of  the  surface  filed,  prevents  to  a  marked  degree  deep 
grooving  and  brings  the  file  under  more  perfect  control. 

When  the  surface  is  narrow  and  a  large  amount  of  metal  is 
to  be  removed  quickly,  the  angle  at  which  the  file  is  held  may  be 
changed,  as  shown  in  Fig.  29.  As  the  contact  area  is  small  in 
this  case  the  bite  is  free.  A  new  file  should  never  be  used  for 
this  purpose,  as  the  teeth  will  take  hold  so  freely  that  they  will 
break  off  or  at  least  lose  their  keen  cutting  edges  very  quickly. 
This  is  much  more  disastrous  on  the  delicate  points  of  the 
double  cut  than  the  long  teeth  of  the  single-cut  files.  Work  of 
this  character  should  be  held  close  down  to  the  top  of  the  vise 
jaws,  thus  preventing  chattering. 

In  selecting  a  file  for  any  piece  of  work  the  form  and  position 
of  the  work  surface  must  determine  the  shape  and  size  of  the  file 


THE    FILE    AND    FILIXC,. 


35 


to  use.  The  hardness  of  the  metal  and  the  amount  of  stock  to  be 
removed,  together  with  the  quality  of  the  finished  surface  that  is 
desired  will  determine  the  degree  of  coarseness  in  the  cut  of  the 
file  used. 

If  the  surface  is  a  flat  one,  the  hand  file,  the  curvature  of  the 
sides  of  which  makes  it  best  suited  to  such  a  surface,  or  its  im- 
mediate associates,  the  flat,  mill  or  pillar  files,  will  be  used.  The 
length  will  depend  upon  the  extent  of  the  surface,  files  shorter 
than  8  inches  being  used  only  on  very  light  work  and  for  the 
heaviest  work  seldom  exceeding  18  inches  in  length. 

If  the  surface  is  an  interior  one,  as  is  the  case  with  the  walls 
of  a  mortise  or  key-way,  the  pillar  or  square  file  will  usually  be 
used.  The  pillar  file  provided  with  one  safety  edge  it  best  suited 
to  this  work  when  the  dimensions  of  the  work  will  admit  of  its 
use.  The  extra  narrow  pillar  can  usually  be  used  in  any  slot 
in  which  a  square  file  of  same  length  can  be  operated.  If  the 


FIG. 


opening  is  very  narrow  a  warding  file  may  be  advantageously 
used.  As  this  file  is  very  thin  and  of  equal  thickness  from  point 
to  heel,  the  operator  must  depend  on  springing  the  file  enough 
to  give  the  required  curvature  for  true  filing. 

In  filing  square  or  round  holes  as  large  a  file  as  can  be  freely 
operated  in  the  openings  should  be  used,  and  if  very  small  a 
slim  square  or  round  may  be  used,  which  gives  the  same  file 
length,  but  smaller  cross-section,  thus  enabling  the  use  of  the 
longest  file  possible.  If  the  hole  is  short  as  compared  with 
the  length  of  the  file,  the  latter  may  be  held  at  point  and  handle 
and  still  allow  enough  length  for  a  suitable  stroke.  When,  how- 
ever, the  hole  is  a  long  one,  the  file  must  be  held  as  shown  in 
Fig.  30.  If  the  round  file  is  materially  smaller  in  diameter  than 
the  hole  it  is  enlarging,  as  shown  in  Fig.  31,  it  will  be  difficult 
to  keep  the  hole  even  approximately  round ;  but  if  larger,  as 
shown  dotted,  better  results  can  be  obtained,  inasmuch  as  the  arc 


MODERN    MACHINE    SHOP    TOOLS. 


of  contact  is  very  much  greater.     Ordinarily  work  of  this  kind 
does  not  require  great  circular  accuracy. 

When  the  curvature  becomes  too  great  to  admit  the  use  of  the 
round  file,  the  half  round  takes  its  place.  With  the  larger  circles 
it  is  not  possible  or  even  desirable  to  have  the  round  side  of  the 


FIG.  31. 


PIG.  32. 


file  fit  the  curve,  but  the  results  required  are  in  such  a  case  ob- 
tained by  giving  the  file  a  side  sweep  on  the  forward  stroke. 
Thus  in  Fig.  32,  when  the  file  is  given  only  a  back  and  forward 
motion,  it  is  impossible  to  maintain  the  smooth'  curve,  but  if, 
as  shown  in  Fig.  33,  the  file  is  swept  sidewise  on  its  forward 


FIG.  33. 

motion  from  A  to  B,  and  after  every  few  strokes  reversed,  so  as 
to  give  the  sweep  from  B  to  A,  thus  causing  the  file  marks  to 
cross  each  other,  true  work  can  be  obtained.  The  file  should,  as 
with  the  hand  file,  be  well  curved  in  its  length,  so  that  any  por- 
tion of  the  surface  may  be  brought  into  action.  It  should  be 


.  34- 


given  a  slight  rotation  in  the  hand  as  it  is  pushed  forward  in  or- 
der that  the  same  high  spot  may  cut  through  the  entire  stroke. 

A  safety  edge  on  a  file  is  oneAhaving  no  teeth.  The  safety  edge 
enables  the  mechanic  to  file  one  of  two  surfaces  A,  intersecting 
at  right  angles,  without  injuring  the  other  B,  as  shown  in  Fig. 
34.  The  safety  edge  on  a  new  file  should  always  be  passed  over 


THE    FILE    AND    FILING. 


37 


a  grindstone  or  emery  wheel  before  depending  on  its  "safety," 
as  in  the  cutting  of  the  sides  the  stock  is  expanded  over  the  edge, 
making  a  slight  concave,  as  shown  at  A,  in  Fig.  35.  While  the 
points  of  the  teeth  do  not,  in  cutting,  form  out  full  over  the 
safety  edge,  the  roots  of  the  teeth  do,  and  they  are  very  apt  to 
scratch  the  surface  the  edge  is  expected  to  protect.  A  very  satis- 
factory safety  edge  is  made  by  grinding  the  teeth  from  the  edge 
of  a  full  cut  file. 

As  the  teeth  of  files  of  rectangular  cross-section  are  not  fully 
formed  at  the  corners,  it  is  not  possible  to  file  a  full  square  with 
them,  since  the  rounded  corners  of  the  file  leave  a  small  fillet  in 
the  angle  of  the  work.  By  grinding  a  safety  edge  on  a  full-cut 
file,  teeth  projecting  to  the  extreme  corner  will  be  obtained,  and 
the  angle  of  the  work  can  be  completely  formed.  As  these  cor- 
ner teeth  are  very  delicate,  they  must  be  used  only  for  the  finish- 
ing strokes,  which  virtually  limits  this  file  to  that  one  operation, 
as  only  the  edge  or  the  side  opposite  the  safe  edge  can  be  used 
for  other  work  without  injury  to  the  corner  teeth.  It  will  usu- 
ally be  found  quite  satisfactory  to  finish  these  corners  with  the 
edge  of  a  small  finely  cut  half-round  file,  used  as  shown  in  Fig. 


FIG.  36. 


FIG.  38. 


36.     By  canting  the  file  slightly  and  using  a  reasonable  amount 
of  care,  good  results  will  be  obtained  in  this  way. 

A  carefully  filleted  corner,  as  shown  in  A,  Fig.  37,  is  difficult  to 
obtain.  A  flat  or  square  file  used  on  surface  C  and  D  is  very 
apt  to  get  into  the  fillet,  and  if  a  safety  edge  is  used,  leaving  the 
work  as  shown  in  B,  Fig.  37,  considerable  difficulty  will  be  had 


38  MODERN    MACHINE    SHOP    TOOLS. 

in  bringing  down  the  corner  with  a  round  file  without  its  cutting 
into  the  faces  C  and  D.  A  flat  file  with  rounded  edges  and  the 
teeth  ground  from  one  side  makes  a  good  file  for  work  of  this 
character  when  the  curvature  of  the  file's  edge  conforms  rea- 
sonably close  with  the  curve  of  the  fillet.  The  faces  C  and  D 
after  being  finished  will  not  be  injured  in  the  use  of  the  safety 
side  file.  The  faces  will  steady  the  tool,  and  its  round  edges  will 
form  the  corners,  it,  of  course,  being  worked  in  from  each  side 
of  the  angle. 

When  the  end  of  a  slot  or  mortise  is  to  be  filed  circular  the 
round  file  usually  does  the  work.  As  there  is  difficulty  in  pre- 
venting the  round  file  from  cutting  into  the  sides  of  the  slot,  it 
will  be  found  advantageous  when  much  of  this  work  is  to  be 
done  to  take  a  round  file  somewhat  larger  in  diameter  than  the 
width  of  the  slot,  and  grind  flats  on  opposite  sides,  making  it 
narrow  enough  to  work  freely  in  the  slot,  as  shown  in  Fig.  38. 
When,  however,  the  ends  of  the  slot  are  formed  by  a  drill  and 
reamer,  and  the  sides  filed  down  to  the  dotted  lines,  as  shown 
in  Fig.  39,  the  edges  of  the  file  should  not  only  be  safe,  but 

rounded,  as  shown,  to  prevent  the 
corner  teeth  from  gouging  into  the 
curved  ends. 

Correct     methods     of     holding 
work  for  filing  must  not  be  over- 
looked.    If  the  work  is  large  and 
1  '  $9 •  heavy,   it  will  simply  require   suit- 

able, rigid  support  to  bring  it  to  the 

proper  height  to  be  operated  upon.  A  very  large  percentage  of  the 
work  will  be  held  in  a  vise.  It  is  important  that  the  work  surface 
be  as  close  down  to  the  top  of  the  jaws  as  possible,  in  order  that 
it  can  be  rigidly  held. 

If  the  work  must  be  held  by  its  finished  surfaces,  smooth  vise 
jaws  should  be  used.  As  it  would  be  impossible  to  keep  the 
jaws  in  this  condition  false  jaws  must  be  used  between  the 
work  and  the  vise  jaws.  These  can  be  made  of  soft  copper  or 
sheet  lead,  pounded  into  the  proper  form  to  fit  nicely  over  the 
jaws.  The  spring  vise  jaw  shown  in  Fig.  40  is 'well  adapted  to 
this  purpose.  Paper  fiber  faces  applied  to  these  jaws  are  ex- 
cellent when  the  surface  of  the  work  caught  is  large  enough  to 
distribute  the  pressure  over  the  face  fairly  well. 

When  a  large  amount  of  bevel  filing  is  to  be  done  some  form 


THE    FILE    AND    FILING. 


39 


of  jig  or  clamp  should  be  used  to  hold  the  surface  filed  in  a 
horizontal  plane,  as  shown  in  Fig.  41. 

If  very  thin  work  is  to  be  filed  on  its  faces,  it  will  not  be  possi- 
ble to  hold  it  in  the  common  vise,  as  the  top  edges  of  the  jaws 


FIG.  40. 


are  usually  worn  rounding,  and  the  work  is  frequently  of  irreg- 
ular outline.  It  may  be  secured  to  a  block  of  hard  wood  by  brad- 
ding  around  its  edges,  and  the  block  held  in  the  vise.  The  brads 
will  file  down  with  the  work,  and  the  flat  surface  prevents  the 
work  from  springing. 

The  term  "draw  filing"  refers  to  that  use  of  the  file  in  which 
.the  direction  of  its  motion  over  the  surface  of  the  work  is  at 
right  angles  to  its  length.  In  draw  filing  the  file  is  grasped  by  its 
ends  with  both  hands,  as  shown  in  Fig.  42.  The  handle  is  usually 


FIG.  42. 


removed,  as  the  file  cannot  readily  be  controlled  when  one  hand 
grasps  the  handle. 

As  the  belly  of  the  file  can  be  brought  to  bear  on  the  high 
spots  more  readily  and  under  better  control  than  in  cross  filing 


4O  MODERN    MACHINE    SHOP    TOOLS. 

more  accurate  results  can  be  obtained  by  draw  filing,  even  by  a 
less  skillful  mechanic.  For  a  given  pressure,  the  file  in  draw 
filing  does  not  cut  so  deep  or  remove  so  much  metal  as  in  cross 
filing.  It  is  not,  therefore,  well  adapted  to  the  quick  removal  of 
large  amounts  of  metal,  but  when  an  accurate  surface  or  a  finely 
finished  one  is  required,  it  can  best  be  obtained  by  draw  filing. 
The  grain  or  lay  of  the  finish  produced  by  draw  filing  will  be  in 
the  direction  of  the  strokes,  and  much  finer  than  can  possibly  be 
obtained  with  the  same  file  in  cross  filing. 

When  a  surface  is  to  be  reduced  wholly  by  filing,  a  second 
cut  or  a  smooth  file  should  be  used  in  cross  filing  to  remove 
the  deep  file  marks  made  by  the  rough  or  bastard  file,  which 
is  used  to  remove  the  bulk  of  the  metal,  thus  producing  a  smooth 
surface  for  the  final  draw-filing  operation.  A  file  coarser  than 
a  second  cut  is  not  suitable  for  draw  filing. 

In  modern  practice  nearly  all  surfaces  that  are  to  be  finished 
are  machined  smooth,  true  and  practically  to  size,  so  that  draw 
filing  alone  will  remove  all  tool  marks  and  prepare  the  surface 
for  polishing,  or  scraping,  if  it  is  to  be  an  accurate  bearing  sur- 
face. In  general,  machined  surfaces  should  be  filed  as  little  as 
possible  in  producing  the  required  finish.  If  filed  too  much,  the 
surface  becomes  untrue,  and  can  be  brought  back  only  at  the 
expense  of  much  time  and  careful  work.  It  is  very  important  in 
machining  surfaces  that  are  to  be  accurately  finished  by  filing 
to  make  the  finishing  cut  a  light  one,  with  the  cutting  tool  so 
adjusted  as  to  leave  a  smooth,  true  surface,  and  thus  requiring 
the  minimum  amount  of  filing. 

After  draw  filing,  the  surface  is  usually  given  a  finish  by  rub- 
bing it  down  with  fine  emery  cloth  and  oil.  For  this  operation 
the  emery  cloth  is  secured  to  a  narrow  block  of  wood,  or  wrapped 
around  the  file.  In  either  case  it  is  given  the  same  motion  as  for 
draw  filing.  When  a  very  fine  finish  is  desired  the  surface  is 
first  draw  filed  in  the  direction  of  the  lay  of  the  final  finish,  with 
a  smooth  file.  The  direction  of  the  strokes  is  now  changed  to 
right  angles,  with  the  required  finish,  a  dead  smooth  file  being 
used.  This  latter  cut  serves  to  level  of!  the  tops  of  the  small 
ridges  left  by  the  first  filing.  The  final  finish  will  be  obtained 
by  rubbing  the  fine  emery  and  oil  over  the  surface  in  the  direction 
of  the  first  filing.  A  piece  of  clean  leather,  charged  with  washed 
emery  and  oil,  is  excellent  for  this  purpose. 

When  a  concave  surface  is  to  be  draw  filed,  the  half  round 


THE    FILE    AND    FILING.  4! 

smooth  or  second  cut  file  should  be  used.,  as  shown  in  Fig.  43. 
The  file  should  be  rotated  slightly  in  the  hands,  so  as  to  bring 
different  portions  of  its  surface  into  action.  It  is  best  to  give  it 
a  small  amount  of  end  motion,  just  enough  to  cause  the  file  marks 
to  cross  each  other. 

In  draw  filing  convex  or  cylindrical  surfaces,  a  flat  file  or  the 
flat  side  of  a  half-round  file  will  usually  be  used.  Such  surfaces 
are  generally  so  filed  to_produce  finish  only,  and  when  cylindrical 
truth  is  required  must  be  very  carefully  done.  As  shown  in  Fig. 
44  the  file  surface  in  contact  with  the  wrork  is  very  narrow,  and 
consequently  the  pressure  on  the  file  must  be  very  light.  As 
shown  by  the  dotted  lines,  the  angle  of  the  file  with  the  horizontal 
should  change  slightly,  yet  a  uniform  amount,  with  each  stroke. 

In  the  draw-filing  operations  the  work  should  be  done  on  the 


FIG.  43.  FIG.  44- 

forward  stroke,  the  file  being  relieved  of  all  pressure,  but  not 
raised  from  the  surface  of  the  work,  on  the  return  stroke. 

In  the  filing  of  rotating  work,  as  between  centers  in  a  lathe, 
there  is  danger  of  too  high  a  cutting  velocity.  This  is  especially 
true  when  the  diameter  of  the  work  is  large.  The  tooth  of  a  file, 
like  any  other  cutting  tool,  will  give  down  if  made  to  do  its 
work  too  fast.  As  practically  all  filing  of  this  class  is  upon  work 
that  has  previously  been  machined  round  and  smooth,  files  coarser 
than  the  second  cut  are  little  used,  the  smooth  meeting  most 
requirements. 

This  class  of  filing  operation  is  for  two  general  purposes  ;  first, 
to  reduce  by  a  small  amount  the  diameter  of  the  work,  and 
second,  to  finish  or  prepare  its  surface  for  finish.  When  accurate 
cylindrical  truth  is  required,  it  is  very  important  that  only  a  small 
amount  of  filing  be  done  on  the  work,  as  it  is  impossible  to  file 


42  MODERN    MACHINE    SHOP    TOOLS. 

any  considerable  amount  from  its  surface  without  throwing  it  out 
of  round.  The  finishing  cut  in  the  machining  should,  therefore, 
be  as  smooth  as  possible,  and  very  close  to  the  exact  finish  diam- 
eter. The  danger  of  filing  work  out  of  round  increases  as  the 
speed  of  rotation  decreases.  That  is,  if  the  work  is  of  small 
diameter  and  makes  a  number  of  revolutions  per  stroke  of  the 
file,  the  surface  will  be  nearer  round  than  when  only  a  few  turns 
are  made  per  stroke.  When  the  work  diameter  is  large,  making 
the  rotation  slow,  it  is  practically  impossible  to  file  equal  amounts 
from  all  parts  of  the  surface,  inasmuch  as  parts  of  the  surface 
of  the  work  are  quite  certain  to  come  under  the  action  of  the 
file  more  frequently  than  others.  It  is  best  in  filing  this  class 
of  work  to  give  the  file  a  comparatively  slow  stroke,  and  as  long 
a  one  as  possible. 

It  must  be  remembered  that,  ordinarily,  the  motion  of  the  file 
to  the  work  in  cross,  or  draw  filing,  is  comparatively  slow — say 
forty  strokes  per  minute  of  perhaps  eight  inches  each.  As  the 
file  is  cutting  only  about  one-half  of  the  time,  the  actual  velocity 
of  cut  in  such  a  case  would  be  not  far  from  fifty  feet  per  minute. 
The  intermittent  motion  of  the  cut  prevents  the  teeth  from  be- 
coming extremely  hot. 

In  filing  revolving  work,  the  number  of  strokes  per  minute 
will  not  be  so  great,  but  the  length  of  the  stroke  will  be  some- 
what increased.  This  will  give  practically  the  same  cutting^ 
speed,  due  to  the  motion  of  the  file,  as  in  cross  filing.  To  this 
must  be  added  the  velocity  of  the  work  surface  under  the  file, 
which  will  vary  from  fifty  to  one  hundred  feet  per  minute.  In 
cross  filing  stationary  work,  only  a  short  length  of  the  file's  sur- 
face is  cutting  throughout  the  stroke,  which  concentrates  the 
work  on  relatively  few  teeth.  In  the  filing  of  rotating  work, 
however,  nearly  all  of  the  file's  length  is  brought  into  action  at 
each  stroke,  which  offsets  largely  the  disastrous  effect  on  the 
teeth,  due  to  too  high  a  cutting  velocity. 

The  file  must  not  be  held  stationary,  allowing  the  work  to 
revolve  to  it,  as  in  that  case  a  few  teeth  do  all  the  cutting,  and 
a  grooved  surface  is  quite  certain  to  result.  The  file  should 
be  held  as  for  cross  filing,  Fig.  23,  and  should,  as  it  is  moved 
forward  over  the  surface  of  the  work,  be  given  a  small  amount 
of  lateral  motion.  If  a  large  amount  of  metal  is  to  be  removed 
the  file  should  be  pushed  diagonally  over  the  work,  as  shown  in 
Fig.  45,  the  direction  of  the  stroke  being  frequently  changed, 


THE    FILE    AND    FILING. 


43 


thus  causing  the  file  marks  to  cross  each  other,  which,  as  pre- 
viously explained,  causes  the  file  to  cut  more  rapidly  and  pro- 
duce a  truer  surface  than  when  continually  moved  in  one  direction. 
When,  however,  a  nice  finish  is  required,  the  stroke  should  be  at 


right  angles  to  the  axis  of  the  work,  as  shown  in  Fig.  46,  and" 
should,  as  indicated  by  dotted  lines,  be  kept  parallel  to  this  posi- 
tion, in  its  sweep  from  left  to  right. 

In  filing  rotating  work,  as  in  the  draw  filing  of  cylindrical 
surfaces,  the  number  of  teeth  in  contact  with  the  work  surface  at 


FIG.  46. 

any  instant  is  relatively  small,  consequently  less  pressure  is  re- 
quired to  make  the  file  bite,  other  things  being  equal,  than  in  the 
filing  of  plane  surfaces.  This  feature  also  enables  the  use  of  files 
on  rotating  work,  which,  due  to  their  concave  surfaces,  could 


44  MODERN    MACHINE    SHOP    TOOLS. 

not  be  used  on  plane  work.  This  affords  an  excellent  oppor- 
tunity for  using  up  those  files,  or  parts  of  files,  which,  owing 
to  their  warped  condition,  are  unfit  for  careful  work  on  plane 
surfaces. 

In  filing  the  face  of  a  rotating  disk  the  same  care  in  the  selec- 
tion of  the  file  must  be  used  as  for  work  on  a  stationary  plane 
surface,  only  the  high  spots  being  available  for  this  purpose. 
This,  unlike  the  work  on  the  cylindrical  surface,  concentrates 
the  work  on  a  small  portion  of  the  file's  surface,  and  consequently 
the  velocity  of  the  work  should  be  lower.  For  this  class  of  filing 
the  file  must  be  held  firmly,  to  overcome  its  tendency  to  move  in 
and  out  on  a  radial  line. 

In  the  filing  of  all  rotating  work,  and  especially  work  having 
projections  or  irregularities,  care  must  be  exercised  to  prevent  the 
file  from  catching  in  the  work.  For  this  purpose  a  file  without 
a  handle  should  not  be  used,  as  in  the  case  of  its  catching  it  is 
very  apt  to  drive  back,  forcing  the  tang  into  the  operator's  hand 
or  wrist.  Frequently,  when  the  character  of  the  work  necessitates 
filing  up  close  to  the  face  plate,  chuck,  or  driver,  it  will  be  found 
convenient  to  run  the  lathe  backward,  the  operator  standing  at  the 
back  of  the  machine. 

A  file  to  do  its  work  fast  and  well  should  be  kept  free  from 
its  cuttings.  If  the  metal  is  of  a  non-fibrous  nature,  as  with  cast 
iron  or  brass,  the  cuttings  pack  solid  between  the  teeth,  thus 
holding  the  teeth  out  of  the  work  and  preventing  the  file  from 
biting  freely.  A  sharp  blow  of  the  file's  edge  against  the  vise 
back  after  every  few  strokes  will  remove  most  of  these  cuttings ; 
if,  however,  too  many  strokes  are  taken  before  cleaning  they 
lodge  so  finely  that  a  file  brush,  as  shown  in  Fig.  47,  must  be  used 


PIG.  47. 


to  remove  them.  These  brushes  are  usually  made  of  fine  wire 
mounted  in  leather,  and  tacked  to  a  light  wooden  back.  A  stiff 
bristle  brush  serves  this  purpose  well,  and  for  very  fine-cut  files 
is  preferable  to  the  wire. 

In  filing  steel  and  wrought   iron,  the  character  of  the  ma- 


THE    FILE    AND    FILING.  45 

terial  reduces  the  disposition  of  the  cuttings  to  pack  between 
the  teeth ;  but,  under  most  conditions,  a  more  serious  trouble, 
that  of  "pinning"  occurs.  Cuttings  "pinv  when  they  lodge  so 
firmly  that  they  cannot  be  removed  with  the  brush.  Unlike  the 
particles  of  cast  iron,  which  crowd  down  below  the  cutting 
edges  of  the  teeth,  and  do  not  injure  the  work,  but  simply  re- 
tard the  cutting  of  the  tool,  the  pin  usually  stands  well  above 
the  teeth  and  scores  the  work  surface  at  every  stroke.  The  "pin" 
can  usually  be  removed  by  drawing  the  wire  file  brush  firmly 
across  the  surface ;  those  that  resist  this  treatment  being  removed 
by  the  scorer.  The  scorer  is  simply  a  piece  of  soft  wire  flattened 
thin  at  the  point,  and  carried  broadside,  rather  than  edgewise 
across  the  file  surface.  After  a  few  strokes  it  becomes  serrated  and 
constitutes  a  short  tooth  comb,  which  picks  out  the  pins  quite 
easily. 

Pinning  may  be  somewhat  reduced  by  chalking  the  surface 
of  the  file,  which  has  also  the  effect  of  reducing  its  bite.  A  lit- 
tle oil  on  the  file  will  frequently  reduce  the  tendency  to  pin.  It 
should  be  used,  however,  only  on  the  fibrous  metals,  as  it  glazes 
the  surface  of  the  non-fibrous  metals,  making  them  harder  to 
cut. 

Chalk  is  usually  applied  to  a  file  when  a  smooth,  fine  work 
surface  is  desired.  The  effect  of  the  chalk  is  to  prevent  the  teeth 
from  cutting  as  freely  as  when  it  is  not  used,  and  thereby  pro- 
duces about  the  same  result  as  would  occur  if  a  finer  cut  file  had 
been  used.  It  becomes  necessary  to  rechalk  the  file  after  each 
cleaning,  an  operation  requiring  some  time,  and  which  can,  by 
using  the  fine  file,  usually  be  avoided. 

When  oil  has  been  used  on  a  file  it  can  readily  be.  removed  by 
thoroughly  chalking  and  brushing  two  or  three  times,  as  the  chalk 
soaks  up  the  oil  and  leaves  a  dry  surface. 

In  fine  filing  operations,  where  it  is  quite  important  to  know 
the  exact  spot  on  the  work  surface  where  the  file  is  cutting,  the 
surface  can  be  dimmed  after  every  few  strokes  by  passing  the 
palm  of  the  hand  over  it.  The  dry,  soiled  hand  will  deaden  the 
surface  enough  to  clearly  show  where  the  file  cuts  on  its  next  few 
strokes,  and  will  in  no  way  injure  the  cutting  of  the  tool. 

Files  are  frequently  injured  by  improper  care  while  not  in  use. 
When  boxed  at  the  factory  they  are  brushed  over  with  oil  and 
wrapped  in  oiled  paper,  which  prevents  them  from  rusting.  When 
this  oil  has  disappeared  they  will,  if  exposed  to  moisture,  rust 


46  MODERN    MAC  1 1  I  N  K    S  1 1  ( >l>    TOOLS. 

readily.  As  there  is  a  large  exposed  tooth  surface  the  deterioration 
<hu'  to  rust  is  rapid. 

Files  should  never  be  thrown  together  in  a  drawer,  or  even 
allowed  to  come  into  contact  with  each  other,  or  with  other 
tools,  as  the  delicate  edges  of  the  teeth  are  most  easily  broken 
down,  and  the  value  of  the  file  seriously  impaired.  They  should 
be  kept  in  a  drawer,  separated  from  each  other  by  low  partitions, 
and  arranged  according  to  length,  section,  cut  and  condition,  thus 
facilitating  the  selection  of  any  desired  file. 

Any  form  of  file  rack,  in  which  the  file  hangs  from  its  handle, 
is  satisfactory.  The  tendency  is  for  files  to  accumulate,  a  large 
number  that  are  nearly  worn  out  littering  up  the  file  drawer  or 
rack,  injuring  the  good  ones  and  doubling  the  time  required  in 
selecting  a  file  for  any  piece  of  work. 

A  number  of  these  partially  worn  files  are  quite  necessary  in 
the  file  drawer  of  the  mechanic  who  is  engaged  on  work  of  a  gen- 
eral character,  as  he  will  very  carefully  avoid  putting  the  new  or 
better  ones  on  the  hard  scale  of  castings  or  forgings. 

The  machinist  should  at  all  times  exercise  good  judgment  in 
the  selection  of  the  proper  file  for  any  piece  of  work  as  he  cannot 
otherwise  expect  to  get  economical  results  from  the  files  he  uses. 
Except  in  cases  where  his  work  is  all  of  one  character  he  will  ex- 
perience little  difficulty  in  so  selecting  that  he  will  always  be  able 
to  use  his  partially  worn  files  to  good  advantage  on  much  of  his 
work,  thus  saving  the  new  ones  for  the  best  work. 

The  broad  surfaces  of  cast  metals  require  the  sharpness  of 
the  new  file  to  properly  cut  them,  while  the  narrow  surfaces 
are  readily  cut  by  the  somewhat  dulled  teeth  of  the  file  that 
has  seen  a  moderate  amount  of  service.  Steel  arid  wrought  work 
will  reduce  the  file  to  a  condition  where  its  further  use  is  un- 
•economical  except  as  it  may  serve  to  protect  the  better  ones  by 
being  used  for  cutting  thin,  hard  materials  and  removing  fins 
and  scale  from  castings  and  forgings. 

Thin  castings,  and  especially  the  fins  on  them,  are  quite  apt 
to  be  chilled,  making  them  harder  than  the  file,  a  condition  not 
conducive  to  the  health  of  that  tool.  The  sand  must  be  thor- 
oughly removed  from  castings  before  applying  even  the  poorest 
file,  as  otherwise,  the  grindstone  action  will  soon  render  the  file 
absolutely  useless. 

The  sand  can  be  largely  removed  by  brushing,  but  the  scale 
only  by  a  chemical  treatment  which  softens  rather  than  removes 


TJIK   FILM    \M>   HUM,.  47 

It.  This  process,  commonly  known  as  pickling,  consists  in  the 
washing  or  soaking  of  the  castings^  a  blue  vitriol  solution,  or 
dilute  sulphuric  acid.  The  length  of  time  the  casting  should  re- 
main in  contact  with  the  pickling  solution  depends  on  the  strength 
of  the  solution  and  the  degree  of  softness  required.  They  should 
be  thoroughly  washed  off  with  water  when  taken  from  the  bath 
and  after  drying  the  scale  can  be  brushed  with  a  wire  scratch- 
brush  or  rattled  off.  When  the  castings  so  pickled  are  to  be 
finished  on  any  of  their  surfaces  by  painting,  it  is  important  that 
they  are  thoroughly  cleaned,  as  otherwise  the  scale  will  eventually 
flake  off,  taking  the  finish  with  it.  In  such  cases  the  castings 
when  removed  from  the  acid  bath  should  be  thoroughly  soaked 
in  a  neutralizing  bath  of  strong,  hot  soda  or  potash  water.  They 
can  then  be  rinsed  in  hot  water  and  dried. 

Pickling  operations  should  be  performed  in  a  well-ventilated 
room,  or  preferably  in  the  open  air,  as  the  fumes  are  poisonous, 
and  in  the  case  of  sulphuric  acid,  explosive  when  mixed  with  the 
proper  proportions  of  air.  The  pickling  vats  if  of  iron  must  be 
lined  with  sheet  lead.  Vats  of  wood  are  frequently  used,  care 
being  taken  to  protect  the  hoops  or  other  iron  fastenings  from 
coming  in  contact  with  the  solution.  A  wooden  vat  lined  with 
sheet  lead  makes  a  very  satisfactory  combination.  Vessels  of 
glazed  or  vitrified  earthenware  are  suitable  when  the  work  is 
suspended  and  not  thrown  into  the  solution. 

For  cleaning  brass  castings  a  solution  of  nitric  and  sulphuric 
acids  with  water  is  usually  used.  The  common  proportions  are 
i  part  nitric  acid,  2  parts  sulphuric  acid,  and  2  parts  water.  The 
castings  are  left  in  the  solution  but  a  short  time  and  then  thor- 
oughly rinsed  first  in  cold,  and  then  hot  water,  after  which  they 
.are  dried  in  sawdust. 


CHAPTER  III. 

SCRAPERS  AND  SURFACE  PLATES. 

The  scraper  is  a  tool  used  by  machinists  for  producing  truer 
surfaces  than  can  be  produced  by  the  ordinary  planing  and  filing 
processes.  It  is  strictly  a^tool  to  be  used  on  stationary  work,  al- 
though the  distinction  between  it  and  the  hand  turning  tool  used 
by  the  brass  worker  is  not  clearly  drawn. 

The  flat  hand  scraper,  as  usually  formed,  is  shown  in  Fig.  48. 


FIG.  48. 

It  is  forged  from  a  piece  of  flat  steel  of  from  y^  to  1%  inch  in 
width  by  %  to  3-16  of  an  inch  in  thickness.  The  point  is  drawn 
down  so  that  the  end  is  about  1-16  of  an  inch  thick,  as  shown 
in  Fig.  49;  The  flats  should  be  ground  well  back  from  the 


FIG.  49. 


FIG.  51 


point  and  the  end  at  right  angles  to  the  length  of  the  tool,  as 
shown  at  A,  Fig.  49,  thus  making  the  angle  of  the  cutting  edges 
but  slightly  more  than  90  degrees,  as  shown  at  B,  same  figure. 

The  end  should  be  ground  slightly  rounding  in  its  length  to 
prevent  the  corners  from  digging  into  the  work  and  the  tools 
taking  too  broad  a  cut,  which  tends  to  produce  a  waved  or  chat- 
tered surface. 


SCRAPERS    AND    SURFACE    PLATES. 


49 


If  the  end  is  ground  so  as  to  give  one  side  a  keener  cutting 
edge,  as  shown  in  Fig.  50,  this  edge  will  cut  faster,  but  the  surface 
produced  will  ordinarily  not  be  so  smooth  as  in  the  former  case, 
it  being  difficult  to  prevent  the  tools  chattering. 

The  scraper,  including  handle,  should  be  from  10  to  12  inches 
long,  depending  on  the  size  of  stock  and  the  character  of  the 
work  on  which  it  is  to  be  used.  If  too  long  it  will  be  springy  and 
will  not  do  good  work.  As  the  angle  forming  the  cutting  edge 
must  be  kept  very  sharp,  a  high  temper  is  necessary,  and  the  end 
faces  after  being  ground  must  be  oil-stoned  often  in  order  to  make 
the  tool  cut  properly. 

The  double  ended  scraper  shown  in  Fig.  51  is  a  form  fre- 
quently used.  This  scraper  should  be  made  somewhat  longer 
than  the  one  shown  in  Fig.  48,  from  14  to  16  inches  being  about 
right.  The  central  portion,  which  serves  as  a  handle,  should  be 
enlarged  and  knurled,  or  twisted  in  the  forging,  so  as  to  enable 
the  hand  to  grip  it  firmly. 

A  form  of  scraper  shown  in  Fig.  52  is  sometimes  employed  on 
fine  work.  The  disadvantages  of  this  form  arise  from  its  hid- 
den cutting  edge  while  at  work,  and  its  having  but  one  cutting 
edge,  thus  necessitating  more  frequent  grindings  than  with  the 
straight  tool. 

The  scrapers  shown  above  are  suitable  for  use  on  plane  or 


FIG.  52. 


FIG.  53- 


convex  surfaces.  If  a  concave  surface  is  to  be  worked  upon, 
a  scraper  of  semicircular  cross  section,  as  shown  in  Fig.  53,  will 
be  used. 

Frequently  in  scraping  circular  surfaces,  and  more  especially 
in  the  softer  metals,  as  brass  or  babbitt,  a  three-cornered  scraper 
can  be  used  to  advantage.  Such  a  tool  is  shown  in  Fig.  54. 


FIG.  54. 


5<D  MODERN    MACHINE    SHOP    TOOLS. 

The  cutting  edges  are  long  ones,  formed  by  the  intersection  of 
the  sides.  In  its  use  this  tool  is  held  in  both  hands,  by  the 
point  and  handle,  when  the  nature  of  the  work  will  permit,  the 
cutting  edges  being  swept  over  the  surface  of  the  work.  This 
scraper  should  be  tapered  from  the  middle  toward  the  point  and 
parallel  from  the  middle  to  the  heel,  thus  giving  curved  and 
straight  cutting  edges,  which  may  be  used  for  taking  narrow  or 
wide  cuts,  as  the  work  may  require. 

Work  that  is  to  have  surfaces  accurately  fitted  by  scraping 
should  be  carefully  planed.  The  finishing  cuts  should  be  very 
light  ones,  taken  with  a  moderately  fine  feed,  the  work  being 
clamped  as  lightly  as  possible,  to  prevent  its  springing  when 
taken  from  the  planer  table.  The  surfaces  should  be  filed  only 
enough  to  bring  them  to  approximate  planes  and  to  remove  traces 
of  tool  marks. 

The  usual  method  of  producing  a  plane  surface  is  by  compar- 


FIG.  55. 

ing  it  with  a  standard  plane.  Such  a  standard  is  called  a  surface 
plate  and  bears  the  same  relation  to  the  testing  of  plane  surfaces 
that  the  cylindrical  gauges  do  to  the  testing  of  circular  surfaces. 
In  Fig.  55  is  shown  a  pair  of  Brown  &  Sharpe  standard  surface 
plates. 

After  bringing  the  surface  of  the  work  to  an  approximate 
plane  by  planing  and  filing,  and  too  much  care  cannot  be  exer- 
cised in  these  operations,  the  work  is  ready  for  the"  scraper.  A 
thin  coating  of  red  marking  is  rubbed  over  the  face  of  the 
surface  plate.  The  material  used  for  this  marking  is  usually 
Venetian  red  mixed  in  oil.  Red  lead  answers  fairly  well,  but 
separates  too  easily  from  the  oil  and  does  not  spread  as  evenly 
and  thin  as  the  former.  The  marking  can  be  best  applied  to  the 
surface  with  the  fingers  or  the  palm  of  the  hand,  as  the  hand 


SCRAPERS  AND  SURFACE  PLATES.  5 1 

detects  any  dust  or  grit  and  spreads  the  marking  thinner  and 
more  uniformly  over  the  surface  than  can  be  done  with  a  piece 
of  rag  or  a  brush.  The  work  surface  is  now  rubbed  over  the 
surface  plate,  the  high  points  on  the  work  being  shown  by  the 
marking  rubbed  from  the  true  surface  of  the  plate.  These  high 
points,  if  small  and  few  in  number,  may  be  reduced  with  a  fine 
file  until  the  work,  when  moved  over  the  plate,  will  show  fairly 
good  contact.  The  file  should  be  used  up  to  that  point  in  the 
operation  at  which  more  time  would  be  required  to  make  the  file 
cut  on  the  proper  spots  and  sufficiently  light  to  prevent  pitting 
than  would  be  required  to  remove  the  metal  with  a  scraper.  The 
workman's  judgment  must  determine  this  point,  and  much  time 
and  hard  work  will  be  saved  if  his  judgment  is  good.  A  file  hav- 
ing considerable  belly  should  be  used  for  this  purpose. 

The  thickness  of  the  coating  of  marking  will  depend  upon  the. 
condition  of  the  surface,  the  nearer  it  approaches  a  plane  the 
thinner  the  marking  must  be.  If  too  thick  false  bearings  will 
show,  which  lead  to  confusion  and  errors  in  the  scraping.  For 
the  finest  work  it  must  be  rubbed  down  so  thin  as  to  be  scarcely 
visible,  and  the  dark  brown  spots  left  on  the  work  will  then 
show  true  bearing  points.  The  harder  the  surfaces  are  pressed 
together  the  plainer  will  the  marks  appear,  the  higher  ones  look- 
ing the  brightest. 

When  the  work  is  heavy  and  awkward  to  handle  the  surface 
plate  may  be  rubbed  over  it.  After  each  course  with  the  scraper 
the  surface  must  be  remarked.  For  the  first  few  courses  the 
strokes  of  the  scraper  may  be  moderately  long,  never  exceeding 
three-fourths  of  an  inch,  but  as  the  surface  becomes  truer  and 
the  bearing  points  close  together,  the  strokes  must  be  made 
shorter,  being'  careful  not  to  overreach  the  marked  points.  •  Each 
course  must  be  made  at  a  considerable  angle  with  the  preceding 
one,  thus  preventing  the  waved  surface  that  results  from  numer- 
ous cuts  across  the  work  in  one  direction. 

The  scraper  should  be  held  as  shown  in  Fig.  56,  and  pressed 
firmly  to  the  work.  The  pressure  required  depends  upon  the 
hardness  of  the  metal  being  scraped  and  the  condition  of  the 
cutting  edge.  This  must  be  carefully  considered  in  accurate  fin- 
ishing, since  as  the  tool  dulls  the  pressure  must  be  increased  in 
order  to  give  cuts  of  equal  depth. 

The  degree  of  accuracy  required  must  in  every  case  determine 
how  far  the  process  should  be  carried.  For  a  strictly  first  class 


52  MODERN    MACHINE   SHOP   TOOLS. 

job  there  should  be  contact  over  practically  the  entire  surface, 
as  shown  by  the  extremely  thin  coat  of  marking.  Such  surfaces 
are  comparatively  expensive  to  produce. 

When  two  plane  surfaces  are  to  move  over  each  other,  as  so 
frequently  occurs  with  machine  parts,  both  may  be  trued  to  the 
surface  plate,  but  usually  the  nature  of  the  work  will  prevent 
the  use  of  the  plate  on  both,  in  which  case  one  surface  may  be 
trued  to  the  plate  and  the  other  fitted  to  this  surface. 

When  two  plane  surfaces  that  are  not  intended  to  move  over 
each  other  are  to  be  fitted  together  one  should,  if  possible,  be 
trued  to  the  plate  and  the  other  fitted  to  it,  Iput  frequently  in 
such  .cases  it  is  not  possible  to  apply  the  plate  to  either  surface, 
and  usually  motion  of  the  one  surface  over  the  other  cannot  be 


PIG.  56. 

had.  In  such  cases  the  process  known  as  "bedding"  must  be 
used.  When  possible  one  surface  will  be  trued  to  the  plate, 
then  covered  with  marking  and  placed  in  position  over  the 
surface  it  is  to  be  fitted  to,  when  a  sharp  blow  with  a  mallet  or 
soft  hammer  will  cause  it  to  mark  the  high  spots  on  the  latter 
surface.  These  spots  can  be  scraped  away  and  the  process  con- 
tinued until  the  marks  appear  uniform  over  the  entire  surface. 
If  neither  of  the  parts  can  be  applied  to  the  plate,  one  must  be 
machined  and  finished  as  true  as  possible  and  the  other  fitted  to 
it.  This  will,  of  course,  not  give  true  plane  surfaces,  but  in 
nearly  all  cases  where  motion  between  the  surfaces  is  not  ex- 
pected, a  uniform  bearing  is  all  that  is  necessary.  As  before,  the 
coating  or  marking  will  depend  upon  the  condition  of  the  surfaces. 
If  too  heavy  at  any  time  the  force  of  the  blow  will  spread  it  into 


SCRAPERS    AND    SURFACE    PLATES.  53 

the  low  spots,  thus  giving,  false  bearings.  Pedestal  bearings,  con- 
necting rod  brasses  and  similar  parts,  must  usually  be  fitted  in 
this  manner. 

Cylindrical  surfaces,  as  shaft,  spindle  and  pin  bearings,  also 
depend  largely  upon  the  scraper  for  bringing  them  to  their  true 
bearing  surfaces. 

In  such  cases  the  bearing  is  usually  fitted  to  its  spindle,  the 
latter  taking  the  place  of  the  surface  plate.  It  follows  that  if 
the  spindle  is  not  round  a  perfect  bearing  will  not  result.  Since 
in  machine  construction  the  cylindrical  truth  of  all  spindles  must 
be  sufficiently  exact  to  satisfactorily  perform  the  operations  for 
which  the  machine  was  intended,  the  bearings  may  be  so  fitted. 
In  high  grade  machine  construction  the  spindles  are  ground 
and  lapped  cylindrically  true,  thus  enabling  the  skilled  workman 
to  scrape  the  bearings  for  these  spindles  as  accurately  as  he  could 
produce  a  plane  surface  from  a  standard  surface  plate. 

In  the  absence  of  a  standard  plane  a  true  plane  surface  may 
be  originated  in  the  following  manner :  Take  three  plates,  the 
surfaces  of  which  have  been  brought  to  approximate  planes. 
Determine  by  means  of  the  straight-edge  which  of  these  plates 
is  the  nearest  true.  Call  this  plate  A  and  the  others  B  and  C. 
Assume  A  as  a  temporary  standard,  and  fit  B  and  C  to  it.  The 
surface  outline  of  A  is  shown  to  an  exaggerated  scale  in  Fig. 
57.  In  Fig.  58  are  shown  B  and  C  placed  together  after  having 


FIG.  57.  FIG.  58. 

been  fitted  to  A.  If  now  B  and  C  are  fitted  to  each  other,  being 
careful  to  correct  equally  the  error  on  each,  it  is  evident  that 
either  B  or  C  will  be  nearer  a  true  plane  than  A.  Now  select 
one  of  these  plates,  say  B,  as  a  temporary  standard  and  fit  A  and 
C  to  it.  Then  fit  A  and  C  to  each  other  as  before.  Next  select 
C  as  the  standard  and  repeat  the  process.  Each  repetition  of 
this  operation  will  bring  the  surfaces  nearer  to  true  planes,  and 
when  they  finally  interchange,  showing  perfect  contact  between 
any  two,  the  work  has  been  completed. 


54  MODERN    MACHINE    SHOP    TOOLS. 

Surface  plates  are  designed  to  resist  as  much  as  possible  the 
deflection  due  to  their  own  weights.  In  large  plates  this  is  an 
extremely  important  point  in  their  construction.  For  the  final 
finishing  the  plates  could  be  tested  while  standing  on  their  edges, 
but  if  trued  in  this  position  they  would  sag  in  the  center  when 
turned  down.  It  would,  therefore,  be  necessary  to  apply  them  to 
the  work  in  the  same  position  in  which  they  were  finished,  which 
would  be  extremely  awkward. 

A  surface  plate  should  always  rest  upon  three  points  of  sup- 
port and  should  be  kept  in  a  substantial  wooden  box,  from  which 
the  cover  can  be  easily  removed,  exposing  the  surface  when  in  use 
and  protecting  it  when  not  in  use  from  accidents  due  to  articles 
falling  on  and  marring  the  face,  as  well  as  from  the  dust.  When 
not  in  use  the  surface  should  be  kept  oiled  to  prevent  rusting, 
which  would  impair  its  accuracy. 

The  surface  plates  should  be  kept  in  a  temperature  as  uniform 
as  possible  and  not  varying  far  from  that  at  which  the  plate  was 
finished,  as  the  expansion  due  to  changes  of  temperature  is 
very  apt  not  to  be  uniform  and  the  truth  of  the  plate  thereby 
affected. 

In  using  the  plate,  wipe  any  dust  or  grit  from  the  face  before 
applying  the  work,  otherwise  there  is  danger  of  scratching  the 
surface.  A  careful  workman  tests  small  work  on  the  edges  of 
the  plate  rather  than  in  the  center,  and  thus  prevents  dishing 
the  plate  through  wear. 


CHAPTER  IV. 

STANDARDS  OF   MEASURE. 

Modern  methods  of  manufacturing  interchangeable  machine 
parts  necessitate  the  extensive  use  of  standard  gauges.  A  stan- 
dard gauge  is  a  fixed  caliper,  the  distance  between  the  measuring 
surfaces  representing  a  certain  definite  portion  of  the  British  Im- 
perial yard,  which  is  also  the  standard  in  the  United  States.  This 
British  yard  is  the  distance  between  two  very  fine  rulings  on 
polished  gold  plugs  inserted  in  a  certain  bronze  rod  commonly 
referred  to  as  bronze  No.  i,  and  carefully  guarded  within  the 
walls  of  the  Houses  of  Parliament. 

As  changes  in  temperature  affect  the  length  of  the  bar,  the  dis- 
tance between  the  lines  is  standard  at  62  degrees  Fahrenheit.  The 
rulings  on  the  gold  are  so  fine  that  they  are  hardly  visible  to  the 
naked  eye,  necessitating  the  use  of  the  microscope  for  making 
comparisons. 

A  number  of  copies  of  the  British  yard  were  made  for  distri- 
bution among  the  different  governments  and  to  preserve  as  refer- 
ence in  case  of  accident  to  the  original  standard.  Of  these  only 
two,  bronzes  No.  19  and  No.  28  were  exactly  standard,  the  others 
varying  slightly  from  the  original.  Both  of  these  are  retained 
by  the  British  government  as  exact  representations  of  their  stan- 
dard of  measure. 

By  act  of  the  British  Parliament,  the  Imperial  yard  was  legal- 
ized in  1855,  and  the  following  year  copy  No.  n  was  presented  to 
the  United  States  Government.  At  62  degrees  Fahrenheit  No. 
ii  is  .000088  of  an  inch  shorter  than  bronze  No.  i,  and  is  ex- 
actly standard  at  62.25  degrees.  The  temperature  at  which  these 
bronzes  are  standard  is  usually  referred  to  rather  than  the  amount 
of  their  error  at  62  degrees  Fahrenheit. 

The  exact  subdivision  of  this  standard  yard  into  its  thirty-six 
equal  divisions,  each  of  which  represents  one  inch,  and  the  still 
further  divisions  to  the  fraction  of  an  inch  was  a  task  of  no  small 
proportions.  Sir  Joseph  Whitworth  obtained  the  inch  subdivi- 
sion by  making  first  three  end  measure  test  pieces,  each  equaling 
as  near  as  possible  one  foot.  Keeping  these  pieces  continually 
of  equal  length  they  were  worked  down  until  the  three  when 


56  MODERN    MACHINE    SHOP    TOOLS. 

placed  end  to  end  exactly  equaled  the  standard  yard.  By  con- 
tinued subdividing  the  foot  pieces  were  reduced  to  inches.  For 
the  fractional  division  of  the  inch  he  depended  on  the  accuracy 
of  a  screw.  The  enormous  amount  of  time  and  work  required 
to  make  this  subdivision  can  hardly  be  appreciated,  and  when 
completed  the  uncertainty  of  maintaining  the  test  pieces  as  stan- 
dards due  to  the  wear  on  the  measuring  faces  by  the  repeated 
trials  necessary  in  the  comparing  of  working  test  pieces  renders 
the  method  unsatisfactory.  These  uncertainties  were  eliminated 
in  the  method  proposed  by  Prof.  William  A.  Rogers  and  so  ably 
carried  out  by  himself  and  the  Pratt  &  Whitney  Company.  This 
method  substituted  for  the  end  measure  test  pieces  a  graduated 
steel  bar,  thus  making  a  line  measure  reference."  As  working 
gauges  are  made  of  tempered  steel,  it  was  important  that  the  ref- 
erence bar  be  made  of  the  same  material,  since  the  effect  of 
changes  in  the  temperature  affects  to  an  unequal  degree  the  ex- 
pansion of  different  metals.  As  repeated  comparison  with  the 
bronze  standard  would  not  be  practical  or  even  desirable,  it  was 


nil  inn  mil  iiiinmm 


FIG.  59. 

decided  by  the  Pratt  &  Whitney  Company  to  construct  a  hard- 
ened steel  bar,  to  be  graduated  and  compared  with  the  official 
standard,  and  that  this  bar,  when  its  precise  relation  to  the  stan- 
dard was  established,  might  thereafter  be  used  as  a  standard  with 
which  to  compare  steel  gauges  and  tools  necessary  in  the  produc- 
tion of  accurate  interchangeable  work. 

Of  the  five  bars  graduated  and  compared  with  bronze  No.  1 1 
the  shortest,  a  tempered  steel  bar,  6  inches  long  and  y2  inch 
square  in  cross  section  is  the  one  about  which  manufacturing  in- 
terests most  center.  The  upper  surface  of  this  bar  is  ground 
and  polished  to  a  perfect  plane,  and  4  inches  of  its  length  grad- 
uated, as  shown  in  Fig.  59.  The  subdivisions  along  one  edge 
are  inches,  half  inches,  quarters,  eighths  and  sixteenths,  along  the 
opposite  edge,  tenths  and  twentieths  and  through  the  center  a 
series  of  lines  representing  the  exact  bottom  diameter  of  U.  S. 
standard  thread  gauges  from  %  to  4  inches,  with  a  band  of  rul- 
ings immediately  below  of  2,500  per  inch.  These  lines  were  cut 


STANDARDS    OF    MEASURE.  57 

with  a  diamond,  and  are  exceedingly  fine,  being  not  greater  than 
1-25,000  of  an  inch  in  width. 

A  complete  description  of  the  method  employed  for  ruling 
and  comparing  these  bars  with  the  standard,  bronze  Xo.  n,  to- 
gether with  a  description  of  the  Rogers-Bond  comparator,  is  given 
in  a  book  published  by  the  Pratt  &  Whitney  Company,  entitled 
"Standards  of  Length  and  Their  Practical  Application." 

The  most  careful  investigation  of  this  steel  line-measure  bar 
shows  it  to  be  but  five  millionths  of  an  inch  longer  at  62  degrees 
Fahr.  than  1-9  of  the  Imperial  yard.  The  greatest  error  in  any 
of  the  subdivisions  does  not  exceed  1-50,000  of  an  inch.  By 
means  of  microscopes  provided  with  micrometer  eye  pieces  the 
reading  or  comparing  of  lines  on  these  finely  ruled  bars  can  be 
made  with  the  greatest  exactness,  and  at  the  same  time  not  im- 
pair in  any  respect  their  accuracy  by  wear,  as  is  the  case  when 
using  end  measure  standards. 

As  a  measuring  machine,  the  essential  features  of  this  remark- 
able instrument  and  its  working  may  be  briefly  stated  as  fol- 
lows :  Two  accurately  lapped  surfaces  corresponding  to  the  anvil 
and  measuring  point  of  the  common  micrometer  serve  as  caliper 
points,  between  wrhich  the  articles  to  be  measured  are  placed. 
The  measuring  point  is  secured  in  the  end  of  a  sliding  plunger, 
which  carries  in  a  suitable  position  a  small  plate,  upon  which 
is  ruled  a  very  fine  reference  or  setting  line.  Back  of,  and 
capable  of  motion,  parallel  with  the  plunger  is  a  carriage 
mounted  on  suitable  guides.  Secured,  adjustably,  to. this  carriage 
are  two  powerful  microscopes,  each  provided  with  micrometer 
eye  pieces,  by  means  of  which  variations  in  the  setting  as  small 
as  1-60,000  of  an  inch  may  be  read.  The  standard  steel  bar  is  so 
placed  that  one  of  the  microscopes  passes  over  its  surface  when 
the  carriage  is  moved  along  its  guides.  A  spiral  spring  attached 
to  the  measuring  plunger  in  a  suitable  manner  provides  equal 
pressure  of  contact  between  point  and  work  as  between  point 
and  anvil. 

In  operating,  the  surfaces  of  the  measuring  point  and  anvil 
are  brought  into  contact,  the  carriage  is  moved  to  the  point  at 
which  one  microscope  shows  exactly  over  the  line  on  the  plate 
on  plunger,  and  the  other  microscope  is  adjusted  to  read  ex- 
actly on  the  initial  line  of  the  standard  bar.  The  plunger  is  now 
moved  back,  and  the  article  to  be  measured  placed  between  the 
points.  The  carriage  is  now  moved  along  its  way  until  the  first 


5»  MODERN    MACHINE    SHOP    TOOLS. 

microscope  again  reads  on  the  line  on  the  plunger.  The  other 
microscope  will  have  moved  over  the  standard  bar  an  amount 
equal  to  the  distance  between  the  measuring  points,  and  the 
reading  on  the  bar,  with  the  aid  of  the  micrometer  eye  piece  for 
the  minute  subdivision,  will  give  the  exact  measurement  in  terms 
of  the  standard. 

Although  desirable  to  maintain  the  temperature  uniformly  as 
near  62  degrees  Fahr.  as  possible,  it  is  not  necessary  in  the  meas- 
uring of  hardened  steel  articles,  as  the  coefficient  of  expansion 


FIG.  60. 

for  these  and  the  standard  bar  is  the  same.  It  is,  however,  very 
important  that  both  the  article  being  measured  and  the  standard 
bar  be  at  exactly  the  same  temperature. 

In  Fig.  60  is  shown  a  general  view  of  the  Rogers-Bond  com- 
parator, owned  by  the  Pratt  &  Whitney  Company. 

With  this  machine  measurements  guaranteed  correct  to  the 
1-50,000  of  an  inch  are  continually  being  made  in  the  produc- 
tion of  the  standard  gauges  of  this  company,  and  differences  in 
dimensions  as  small  as  1-100,000  of  an  inch  readily  indicated. 
It  will  be  understood,  however,  that  measuring  and  indicating 
are  vastly  different  matters,  as  a  difference  in  dimensions  too 


STANDARDS   OF    MEASURE.  59 

small  to  be  read  with  any  degree  of  accuracy  can  be  readily  de- 
tected. Thus  we  see  that  at  great  expenditure  of  time  and  labor 
a  working  standard,  the  reliability  of  which  is  beyond  question, 
was  produced. 

Standard  gauges  cannot  be  classed  as  measuring  instruments, 
as  they  do  not  determine  the  amount  of  variation  when  they  do 
not  fit  the  work.  If  the  work  is  very  nearly  to  size,  however, 
the  tightness  of  the  fit  will  give  an  idea  as  to  how  much  the  work 
is  over  or  under  size;  this  based  on  the  judgment  of  the  opera- 
tor, of  course. 

In  Fig.  6 1  is  shown  a  plug  and  ring  gauge.  The  diameter  of 
these  gauges  is,  as  stamped  on  them,  iy2  inches,  as  near  as  hu- 
man skill  can  make  them.  The  particular  gauges  shown  are 
guaranteed  correct  to  the  1-50,000  of  an  inch.  It  is  perhaps  dif- 
ficult to  conceive  of  a  dimension  so  small.  Take  i-ioo  of  an  inch, 
which  is  the  smallest  graduated  space  commonly  put  on  the 
ordinary  steel  scale.  Imagine  this  small  distance  divided  into 


FIG.  61.  FIG.  62. 

ten  equal  parts,  and  then  one  of  these  portions  into  fifty  equal 
parts,  and  you  really  have  something  small  in  the  way  of  distance. 
Although  so  nearly  of  the  same  size,  by  skillful  manipulation,  the 
plug  may  be  made  to  enter  the  ring.  Both  surfaces  must  be 
wiped  perfectly  clean  and  coated  with  fine  oil.  When  entered  the 
one  will  move  over  the  other  with  great  smoothness  and  surpris- 
ing ease,  but  if  the  motion  is  stopped  for  only  an  instant  they  will 
set,  and  so  firmly  that  nothing  short  of  a  sharp  blow  with  a  mallet 
will  start  them.  There  can  certainly  be  but  little  room  for  lubri- 
cation between  these  surfaces,  and  the  supposition  is  that  when 
motion  stops  the  little  globules  of  oil  flatten  out  so  thin  that  the 
surfaces  of  the  metal  coming  into  contact  grip  each  other.  The 
effects  of  temperature  are  clearly  shown  by  first  cooling  and  then 
warming  slightly  the  plug.  In  the  first  case  it  enters  the  ring 
readily  and  in  the  latter  it  cannot  be  induced  to  start.  These 
gauges  are  made  in  any  desired  sizes,  from  14  to  6  inches. 

In  Fig.  62  is  shown  an  end  measure  test  piece.     This  little 


6O  MODERN    MACHINE    SHOP    TOOLS. 

piece  of  hardened  steel  measures  exactly  between  faces  the  dis- 
tance stamped  on  it.  The  small  hole  in  the  side  is  to  receive 
a  small  wooden  handle  with  which  to  manipulate  it,  as  the  heat 
from  the  fingers  would  otherwise  affect  its  length. 

The  accuracy  of  the  method  of  making  and  the  final  meas- 
uring of  these  test  pieces  were  shown  most  conclusively  by  the 
severe  test  of  the  committee  of  the  American  Society  of  Mechan- 
ical Engineers  appointed  to  investigate  the  subject  of  standards 
and  gauges.  The  test  consisted  of  the  placing  end  to  end  in  a 
groove  planed  in  a  heavy  block  of  cast  iron,  Pratt  &  Whitney 
end  test  pieces  of  miscellaneous  lengths  aggregating  a  total 
length  of  12  inches,  between  suitable  stops  which  were  so  ad- 
justed that  a  14-inch  end  measure,  used  as  a  try  piece,  was  held 
with  just  sufficient  friction  to  allow  it  to  move  easily.  Twelve 


JUT 


INTERN  AL. 


EXTERNAL. 

FIG.  63.  PIG.  64. 

different  sets,  all  of  which,  had  been  resting  on  the  block  of  iron 
sufficiently  long  to  attain  the  same  temperature  were  tried  be- 
tween the  stops.  Each  set  was  made  up  of  different  combinations 
of  lengths  using  in  each  case  the  same  ^4-inch  try  piece.  With 
one  exception  these  twelve  sets  were  found  .to  be  of  uniform 
length,  the  try-piece  fitting  with  practically  the  same  fric- 
tion in  each  of  the  eleven  sets.  In  one  case  where  the  try- 
piece  was  quite  loose,  it  was  found  that  the  total  length  of  the 
pieces  was  i- 10,000  of  an  inch  short,  most  of  this  error  being  in 
one  piece,  which  had  been  previously  rejected  because  of  a  defec- 
tive face. 

Fig.  63  shows  a  form  of  caliper  gauge,  double  end  pattern, 
for  gauging  both  internal  and  external  dimensions.  For  the 
larger  sizes  the  forms  shown  in  Fig.  64  are  used,  as  they  make 


STANDARDS    UF    MEASURE. 


61 


lighter  and  more  convenient  tools.  For  general  shop  use,  where 
constant  reference  is  to  be  made  to  them,  these  gauges  are  pref- 
erable to  the  plug  and  ring  forms,  being  lighter,  cheaper  and 
more  convenient.  With  the  ring  gauge  it  must  be  applied  to  the 
end  of  the  work,  while  the  external  caliper  gauge  can  be  used 
at  any  point  in  the  length  of  the  work. 

Good  judgment  must  be  exercised  in  the  use  of  all  accurate 
gauges.  They  must  never  be  forced,  as  in  that  case  excessive 
wear  results,  and  they  soon  become  unreliable.  A  standard  ring 
is  not  intended  for  measuring  anything  except  work  that  by  care- 
ful methods  has  been  brought  to  the  gauging  diameter.  It 
should  move  freely  over  the  work  without  forcing,  and  yet  close 
enough  to  show  no  shake.  When  it  is  considered  that  1-2000 
of  an  inch  is  the  difference  between  a  tight  and,  a  loose  fit,  the 
results  possible  with  gauges  of  this  character  become  evident. 


FIG.  65. 


In  using  the  external  caliper  gauge,  if  forced  over  the  work  not 
only  wear  to  the  faces,  but  springing  of  the  jaws  will  result,  both 
of  which  destroy  the  accuracy  of  the  tool.  Never  attempt  to  use 
this  or  any  other  gauge  on  rotating  work,  as  the  faces  will  catch 
and  draw  over  work  several  thousandths  over  gauge  size. 

In  the  machining  of  nearly  all  work,  a  certain  amount  of 
variation  from  the  exact  standard  size  is  permissible,  the  amount 
of  this  variation  depending  on  the  nature  of  the  work.  If,  for 
example,  the  variation  allowed  in  the  making  of  a  large  number 
of  like  parts  was  .001  of  an  inch  from  exact  size,  the  economical 
production  of  these  articles  would  not  permit  the  loss  of  time  in 
making  them  unduly  accurate. 

The  gauges  shown  in  Figs.  65  and  66  illustrate  external  and 
internal  limit  gauges.  One  end  of  the  external  gauge  shown 


62 


MODERN    MACHINE    SHOP    TOOLS. 


must  pass  over  work  not  exceeding  .250  of  an  inch  in  diameter. 
The  opposite  end,  which  is  but  .0015  of  an  inch  smaller,  must 
not  go  over.  In  this  case  the  limit  is  all  under  the  exact  size, 


FIG.  66. 

while  in  the  internal  gauge  shown  in  Fig.  66  the  limit  of  .002 
is  half  below  and  half  above  the  standard  size. 

In  Fig.  67  are  shown  United  States  standard  thread  gauges, 


FIG.  67. 

external  and  internal.  By  an  extremely  accurate  method,  the 
threads  of  these  gauges  are  ground  after  hardening,  which  leaves 
them  highly  finished  and  correct  as  to  pitch  and  angle.  The  stan- 
dard pipe  gauge  is  illustrated  in  Fig.  68.  The  use  of  standard 


FIG.  68. 


FIG.  69. 


thread  gauges  enables  the  manufacturer  of  pipe,  fittings,  screws, 
etc.,  to  maintain  standard  threads  and  sizes  by  referring  all  taps 
and  dies  to  the  standards. 

The  corrective  gauge  shown  in  Fig.  69  is  used  for  testing  the 


STANDARDS   OF    MEASURE.  63 

correctness  of  caliper  gauges.  To  insure  against  errors  aris- 
ing from  the  use  of  gauges  which,  through  wear  or  accident, 
have  become  incorrect,  it  is  important  that  they  frequently  be 
referred  to  the  corrective  gauge.  Caliper  gauges  which  have 
worn  on  the  faces  until  they  are  oversize,  can  be  brought  up  to 
standard  by  pening  lightly  the  outer  edge  of  the  crescent. 

The  use  of  standard  gauges  and  micrometers  has  done  much 
to  systematize,  improve  and  lessen  the  cost  of  many  lines  of 
manufacture.  With  our  present  excellent  systems  of  gauging 
it  would  be  quite  possible  to  build  the  many  parts  of  a  steam 
engine  or  machine  tool  in  many  different  shops  throughout 
the  country  and  to  assemble  these  parts  into  a  perfect  working 
machine. 

In  the  manufacture  of  gauges  the  cost  depends  very  largely  on 
the  degree  of  accuracy  obtained.  A  set  of  cast  iron  plugs  and 
rings  for  common  work  can  be  ground  correct  to  one-fourth  of 
a  thousandth  without  much  trouble.  But  when  of  tempered  steel 
and  the  error  reduced  from  1-4,000  to  1-50,000  of  an  inch,  the 
cost  of  production  due  to  this  great  refinement  increases  many 
times. 

Gauges  that  are  to  be  finished  to  the  highest  possible  degree  of 
accuracy  are,  after  being  hardened,  ground  to  nearly  the  required 
dimensions,  and  then  stored  away  to  "season."  Gauges  that  are 
finished  immediately  after  hardening  will  frequently  crack  open 
several  months  later.  It  has  been  found,  however,  that  if  the 
gauge  is  allowed  to  stand  for  about  a  year  before  the  finishing 
work  is  done  on  it,  it  is  not  apt  to  crack  thereafter.  Gauges  are 
made  standard  at  62  degrees  Fahrenheit. 


CHAPTER   V. 

CALIPERS. 

Calipering  tools  may  be  classed  under  two  heads — transfer  and 
recording.  The  transfer  class  includes  all  calipers  used  to  trans- 
fer scale  dimensions  to  the  work,  work  dimensions  to  the  scale, 
or  to  receive  and  transfer  from  one  piece  of  work  to  another  a 
dimension  without  reference  to  its  exact  magnitude.  The  record- 
ing caliper  is  provided  with  a  scale  which  gives  the  length  of 
the  dimension  measured  as  well  as  forming  a  transfer  instru- 
ment. This  latter  class  includes  the  vernier  and  micrometer 
calipers.  The  large  and  heavy  calipers  of  this  class  are  called 
"bench  micrometers/'  Recording  calipers  are  usually  graduated 
to  read  to  one-thousandth  of  an  inch,  which  makes  them  suffi- 
ciently accurate  for  use  on  all  ordinary  mechanical  operations. 
When,  however,  the  tool  is  designed  for  greater  accuracy,  it 
becomes  necessarily  more  delicate  and  expensive,  and  is  not 
suitable  for  general  shop  work.  Such  instruments  come  under 
the  class  known  as  "measuring  machines,"  which  are  used  as 
test  instruments. 

The  transfer  calipers  are  of  three  general  forms:  firm  joint, 
lock  joint  and  spring,  the  latter  two  usually  being  called  adjust- 
able calipers. 

Calipers  to  be  first-class  should  have  well  proportioned  legs 
made  of  high  grade  steel,  preferably  tempered,  with  a  carefully 
fitted  joint  having  a  uniform  amount  of  friction  at  all  positions 
of  the  legs,  thus  insuring  a  smooth,  steady  motion  when  setting. 

In  Fig.  70  are  shown  at  A  and  B  a  pair  each  of  outside  and 
inside  firm  joint  calipers,  and  at  C  a  pair  of  inside  lock  joint  cal- 
ipers. In  this  tool  a  tapered  socket  joint  enables  the  short  arm 
A  to  be  rigidly  locked  with  the  outside  leg  B  by  tightening  the 
knurled  nut  C.  The  nut  D,  which  is  coned  on  the  bottom,  moves 
over  a  stud,  which  is  secured  in  the  middle  leg,  and  moves 
through  a  slot  in  A.  Secured  to  A  is  a  small  cone,  against 
which  the  cone  nut  bears,  thus  forcing  the  middle  leg  away  from 
A  when  D  is  tightened  down.  A  stiff  spring  set  in  the  under  side 
of  A  resists  the  separation  and  holds  the  joint  steady.  This  tool 
may  be  set  to  approximately  the  size  desired,  the  joint  locked 


CALIPERS.  65 

and  the  final  adjustment  obtained  by  turning  the  nut  D.  By  ad- 
justing C  to  give  the  correct  friction  this  tool  may  be  used  as 
a  firm  joint  caliper. 

At  D,  Fig.  70,  is  shown  a  good  example  of  the  numerous  forms 
of  spring  calipers  in  use.  Its  construction  is  clearly  shown  in 
the  figure.  They  may  be  had  with  solid  or  slip  nut  on  the  screw, 
a  slip  nut  being  shown  at  E,  Fig.  70.  It  is  a  split  nut  pivoted  at  A 
with  a  light  spring  in  a  recess  inside  the  knurled  head,  which 
holds  the  halves  together  at  the  threaded  end,  the  outside  of 
which  is  coned  to  fit  a  recess  in  the  post  or  caliper  leg,  which 
prevents  the  nut  from  opening  when  the  tension  of  the  joint 
spring  is  upon  it.  The  slip  nut  saves  time  in  setting  the  calipers, 


which  is  of  material  importance  where  numerous    settings  are  to 
be  made. 

The  skillful  use  of  transfer  calipers  depends  entirely  on  the 
good  judgment  and  delicate  touch  of  the  operator.  He  must 
recognize  contact,  between  the  points  of  the  caliper  and  the 
work,  without  pressure.  The  ability  to  make  a  sure  calipered 
fit  is  an  accomplishment  that  comes  only  with  practice.  In  set- 
ting calipers  to  a  scale  care  must  be  exercised,  the  chance  for 
personal  error  being  great.  In  setting  the  outside  calipers  the 
scale  should  be  held  vertically  in  the  left  hand,  with  the  end  of 
the  little  finger  resting  against  the^side  at  the  bottom  end  to 
steady  the  lower  point  of  the  calipers  over  the  end  of  the  scale, 
the  caliper  being  held  in  the  right  hand,  as  shown  in  Fig.  71. 
If  the  caliper  is  a  "firm  joint"  it  must  be  adjusted  to  the  re- 
quired dimension  by  tapping  the  legs  against  some  solid  body, 
the  force  of  the  blow  diminishing  until  the  proper  adjustment 
is  obtained.  In  setting  the  adjustable  calipers,  they  should  b^ 


66 


MODERN    MACHINE    SHOP    TOOLS. 


held  in  the  right  hand,  as  shown  in  Fig.  72,  the  thumb  and  fore- 
finger operating  the  adjusting  nut.  The  upper  caliper  point 
rests  against  the  side  of  the  scale  and  over  the  graduations.  The 
lower  point  rests  against  the  end  of  the  scale,  but  the  eye  must 
determine  when  the  upper  point  coincides  exactly  with  the  re- 
quired reading.  The  end  of  the  scale  should  be  square,  only  a 


FIG.  71. 

comparatively  new  steel  scale  being  suitable,  as  an.  old  one  is 
frequently  worn  enough  to  make  it  appreciably  short.  When 
the  caliper  is  heavy  the  little  finger  of  the  right  hand  should 
be  pressed  against  the  lower  leg  to  steady  and  support  it.  The 
slight  angularity  of  the  points  with  the  plane  of  the  scale,  due 
to  dropping  the  lower  point  below  the  graduated  surface,  has 


FIG.  72. 


an  appreciable  effect  on  the  accuracy  of  the  setting  only  when 
adjusting  for  the  smaller  dimensions.  This  error  may  be  avoided 
by  slightly  twisting  the  caliper  so  as  to  spring  the  legs  sidewise 
enough  to  bring  the  points  in  planes  parallel  to  the  surface  of  the 
scale. 


CALIPERS.  67 

In  setting  the  inside  calipers  to  the  scale  the  end  of  the  scale 
should  be  placed  against  and  held  at  right  angles  to  a  plane  sur- 
face ;  one  point  of  the  caliper  placed  against  this  surface  and  the 
other  adjusted  to  the  required  reading  on  the  scale.  It  is  very 
important  that  the  scale  be  held  perfectly  at  right  angles,  as  a 
slight  variation  makes  considerable  error  in  the  reading.  It  is 
not  good  practice  to  set  both  points  to  lines  on  the  scale,  as  the 
chance  for  error  is  much  greater  than  when  the  measurement  is 
referred  to  one  end  of  the  scale. 

In  transferring  a  setting  from  one  pair  of  calipers  to  another, 
the  reference  pair  should  be  held  in  the  left  hand,  with  the 
lower  point  resting  against  the  end  of  the  little  ringer.  The  lower 
point  of  the  pair  being  set  should  be  brought  in  contact  with 
this  point,  the  end  of  the  finger  serving  to  steady  the  points.  The 
upper  point  should  then  be  so  adjusted  that  it  just  makes  contact 
with  the  upper  point  of  the  reference  pair.  The  accuracy  attained 
depends  entirely  upon  the  skill  with  which  this  adjustment  is  made, 
other  than  the  slightest  pressure  between  the  points  serving  to 
distort  the  measurement. 

Assume  that  a  shaft  is  to  be  turned  to  4^  inches  in  diameter 
and  a  hub  bored  to  fit  this  shaft.  The  outside  caliper  will  be  set 
to  size,  as  shown  in  Fig.  71,  involving  the  first  chance  for  error. 
The  bar  will  now  be  turned  and  finished  to  the  caliper  size,  allow- 
ing a  second  chance  for  error.  The  third  opportunity  for  error 
arises  in  the  setting  of  the  inside  to  the  outside  calipers,  and 
finally  the  fourth  in  boring  the  hub  to  the  dimension  of  the  in- 
side caliper.  Of  these  the  first  two  affect  the  diameter  of  the 
work  and  the  last  two  the  fit. 

In  using  the  outside  calipers  they  must  pass  squarely  over  the 
work,  just  touching  it.  The  lighter  the  touch  the  greater  the 
accuracy  attainable.  For  final  calipering  the  work  must  be  sta- 
tionary, as  a  rotating  piece  will  draw  the  calipers  over  long  be- 
fore they  are  down  to  size.  When  a  number  of  pieces  are  to  be 
turned  to  sample,  it  is  permissible  to  set  the  calipers  so  that  the 
contact  will  just  sustain  their  weight,  turning  all  of  the  pieces 
so  the  contact  will  be  the  same.  This,  however,  can  hardly  be 
called  calipering. 

In  setting  the  inside  calipers  to  the  outside,  the  contact  be- 
tween points  should  be,  as  near  as  a  delicate  touch  can  deter- 
mine, the  same  as  the  contact  between  outside  caliper  points  and 
the  work.  The  work  should  then  be  bored  to  that  diameter 


68 


MODERN    MACHINE    SHOP    TOOLS. 


which  gives  the  same  contact  between  the  inside  calipers  and  the 
walls  of  the  hole  as  between  the  inside  and  outside  calipers. 

The  caliper  shown  at  A  in  Fig.  73  is  technically  known  as  a 
"transfer"  caliper.  Frequently  it  is  necessary  to  caliper  a  piece 
of  work  the  shape  of  "which  makes  it  impossible  to  remove  the 
calipers  without  loosing  the  setting.  In  this  tool  the  leg  A  is 
•secured  to  the  blade  B  by  the  stud  and  nut  C,  the  stud  striking 
against  the  end  of  the  small  slot.  The  caliper  is  then  set,  for 
example,  to  the  larger  diameter  of  a  chambered  cylinder,  and  the 
joint  nut  tightened,  securing  D  and  B  to  each  other.  C  can  now  be 
loosened  and  the  leg  A  moved  to  allow  the  tool  to  be  removed 
from  the  work.  When  moved  back  against  its  stop  it  will  show 
the  original  setting.  Only  calipers  of  the  very  best  construction 
should  be  depended  upon  for  this  kind  of  work. 


FIG.  7; 


The  thread  caliper  is  shown  at  B  in  Fig.  73.  It  has  \vide,  thin 
points  for  calipering  both  the  top  and  bottom  of  screw  threads. 

At  C,  Fig.  73,  is  shown  a  hermaphrodite  caliper,  a  tool  having 
one  caliper  and  one  divider  leg.  The  divider  leg  is  preferably 
adjustable,  and  when  caliper  is  of  the  spring  pattern  the  caliper 
leg  must  have  right  and  left  feet,  as  the  legs  cannot  pass  by  each 
other  as  writh  the  firm  or  lock  joint  patterns.  This  caliper  is  a 
valuable  tool  for  centering,  and  scribing  purposes. 

The  key  hole  caliper,  shown  at  D  in  Fig.  73,  is  a  valuable 
tool  on  work  the  shape  or  position  of  which  will  not  allow  the  use 
of  two  curved  legs. 

The  vernier  caliper,  an  example  of  which  is  shown  in  Fig.  74, 
is  a  form  of  beam  caliper  which  depends  for  its  setting  on  a 
graduated  scale  on  the  side  of  the  beam,  the  subdivision  of  the 


CALIPERS.  69 

graduation  on  the  beam  being  obtained  by  means  of  the  ver- 
nier on  the  sliding  jaw.  This  tool  possesses  the  advantage  of 
wide  range  and  comparatively  light  weight.  Its  value  as  a  measur- 
ing instrument  depends  on  its  accuracy  of  construction,  cheap 
calipers  of  this  class  being  of  little  value.  The  jaws  should  be  of 
tool  steel,  carefully  tempered,  and  the  faces  ground  exactly  parallel 
with  each  other.  The  sliding  jaw  is  given  its  final  adjustment  by 
means  of  the  small  knurled  nut  and  screw  in  the  auxiliary  slide. 
The  graduations  usually  read  to  thousandths  on  the  front  side  of 
the  beam,  and  to  sixty-fourths  on  the  back.  They  may  be  r.secl 
for  either  inside  or  outside  measurements,  but  for  inside  readings 
on  the  vernier  side  a  constant  equal  to  the  space  occupied  by  the 
points  must  be  added.  On  the  back  side  of  the  instrument  two 
zero  lines  are  used,  one  for  inside  and  one  for  outside  measure- 
ments, thus  avoiding  the  necessity  of  the  addition  for  the  inside 
readings. 

In  explanation  of  the  use  of  the  vernier :  Referring  to  Fig.  74, 


FIG.  74. 

it  will  be  noted  that  the  scale  on  the  beam  is  divided  into  inches, 
tenths  and  fiftieths,  and  that  twenty  divisions  on  the  vernier 
cover  exactly  nineteen  divisions  on  the  scale.  This  makes  each 
division  on  the  vernier  1-20  of  1-50  less  than  a  division  on  the 
scale,  or  i-iooo  of  an  inch.  In  the  figure  the  zero  on  the  vernier 
stands  at  .2  inch ;  if,  now,  the  sliding  jaw  was  moved  out  until 
the  10  on  the  vernier  coincided  with  the  next  line  on  the  scale 
(.4  inch)  it  would  have  moved  through  10-20  of  1-50  = 
i-ioo  or  .21  inch  from  zero;  and  in  like  manner  if  the  fourteenth 
division  on  the  vernier  had  moved  to  coincide  with  the  third  line 


70  MODERN    MACHINE    SHOP   TOOLS. 

beyond  1.6  inches,  as  shown  in  Fig.  75,  the  reading  would  be 
I  inch  +  .3  inch  +  4-50  (.08)  +  .014  =  1.394  inches. 

Other  graduations  than  the  one  shown  may  be  used;  for 
example,  if  the  beam  is  graduated  into  forty  lines  per  inch  and  the 
vernier  has  twenty-five  divisions  covering  twenty-four  on  the 
scale,  then  each  division  will  be  1-25  shorter  than  one  on  the  scale 
and  1-25  of  1-40  =  i-iooo  of  an  inch. 

A  magnifying  glass  is  of  great  value  in  reading  these  instru- 


FIG.  75. 

ments,  especially  so  when  many  readings  are  to  be  made  in  a  short 
space  of  time,  it  being  very  trying  on  the  eyes. 

The  micrometer  caliper,  a  skeleton  view  of  which  is  shown  in 
Fig.  76,  is  a  tool  that  has  come  into  very  general  use  among 
mechanics  employed  on  work  requiring  uniformity  and  accuracy. 
Its  simplicity  and  relatively  low  cost  make  it  an  instrument  that 


FIG.  76. 

even  the  mechanic  on  comparatively  coarse  work   can   scarcely 
afford  not  to  have  in  the  caliper  drawer  of  his  tool  chest. 

These  calipers  may  be  divided  into  two  classes,  the  yoke  and 
the  beam  patterns,  Fig.  76  illustrating  the  former.  In  this  figure 
the  construction  is  quite  clearly  shown.  The  shank  of  the  yoke 
contains  at  its  outer  end  a  split  nut,  which  for  adjustment  for 


CALIPERS.  71 

wear,  may  be  closed  onto  the  screw  by  advancing  the  nut  toward 
the  yoke,  the  stem  being  threaded  on  a  slight  taper.  The  gradu- 
ated shell  or  thimble  is  attached  to  the  end  of  the  screw  and  rotates 
with  it,  moving  along  and  over  a  shell  on  the  shank.  As  the  screw 
does  not  extend  out  of  the  yoke  it  is  completely  encased  and  pro- 
tected from  dust  or  injury  for  all  positions  of  the  measuring 
point  within  the  range  of  the  instrument.  The  small  knurled  exten- 
sion to  the  thimble  serves  as  a  speeder  for  rapidly  advancing  the 
screw.  The  knurled  nut  in  the  yoke  contracts  a  split  bushing  over 
the  measuring  stem,  thus  locking  it  in  any  desired  position.  The 
measuring  point  and  the  anvil  against  which  it  strikes  are  care- 
fully hardened  and  ground,  making  the  surfaces  parallel  planes. 

The  micrometers  of  this  class  are  usually  provided  with  a 
screw  having  forty  threads  per  inch.  The  barrel  is  graduated  to 
tenths  and  fortieths  of  an  inch.  Thus  one  revolution  of  the 
screw  advances  the  thimble  one  division  on  the  barrel,  which 
equals  1-40  of  an  inch  or  .025  inch.  As  the  circumference  of  the 
thimble  is  divided  into  twenty-five  equal  parts,  1-25  of  one 
revolution  of  the  screw  advances  the  measuring  point  1-25  of 
1-40=  i-iooo  of  an  inch.  When  the  end  of  the  measuring  point 
and  the  anvil  come  in  contact,  the  zero  points  on  barrel  and 
thimble  should  coincide,  thus  avoiding  the  necessity  of  a  cor- 
rection for  each  reading.  As  the  measuring  faces  and  screw  wear 
slightly,  it  is  necessary  to  provide  some  means  of  adjustment  in 
order  to  keep  the  zero  reading  correct.  In  this  particular  instru- 
ment the  barrel  may  be  rotated  on  the  shank  sufficient  to  bring  the 
lines  correct.  In  others  the  anvil  may  be  forced  ahead  by  means 
of  a  small  screw  in  the  yoke. 

As  these  instruments  are  graduated  to  read  decimally,  a  table 
of  decimal  equivalents  is  usually  stamped  on  the  sides  of  the  yoke, 
eighths,  sixteenths  and  thirty-seconds  on  one  side,  and  sixty- 
fourths  on  the  opposite. 

In  Fig.  77  is  shown  a  micrometer  caliper  to  take  sizes  between 
one  and  two  inches.  When  the  zero  points  coincide,  the  face  of 
the  measuring  point  is  exactly  one  inch  from  the  face  of  the 
anvil.  A  i-inch  reference  disc,  hardened,  ground  and  lapped  to 
size  is  furnished  with  each  caliper  with  which  to  test  the  correct- 
ness of  the  setting. 

Although  a  half,  or  even  a  fourth  of  one-thousandth  can  be 
quite  readily  approximated  on  the  reading,  which  brings  it  within 
the  accuracy  limit  of  all  ordinary  work,  it  is  frequently  desirable 


72  MODERN    MACHINE    SHOP   TOOLS. 

to  get  at  these  fine  readings  more  closely.  For  this  purpose  the 
vernier  is  applied  to  the  barrel,  as  shown  in  Fig.  78.  It  consists 
of  ten  parallel  rulings  on  the  barrel,  occupying  the  same  space  as 
nine  of  the  twenty-five  divisions  on  the  thimble,  which  makes  the 
spaces  on  the  barrel  one-tenth  shorter  than  those  on  the  thimble, 


1    .0625 
3  . 1873 
5   .3125 
7    .4375 
9    .5625 
11  .6875 
.13.8125 


FIG.  77. 

thus  giving  i-io  of  1-25  of  1-40=1-10,000  of  an  inch.  This 
refinement  can  be  relied  upon  only  when  the  greatest  care  is 
exercised  in  making  the  measurements,  as  the  slightest  excess  of 
pressure  on  the  screw  over  that  at  which  the  caliper  is  adjusted 
will  spring  the  instrument  more  than  the  minute  distance  it  is 
expected  to  indicate.  Calipers  graduated  to  ten-thousandths  should 


FIG.  71 


be  used  only  where  fine  measurements  are  required  as  the  wear 
due  to  common  use  will  shortly  impair  their  accuracy  for  the  fine 
measurements. 

In  the  use  of  the  micrometer  caliper  it  is  important  that  the 
pressure  of  the  measuring  point  against  the  work  is  the  same  as 
the  pressure  of  the  point  against  the  anvil  when  the  zero  setting 
is  made,  as  it  is  quite  possible  for  a  careless  workman  to  force  the 
screw  enough  to  set  the  thimble  zero  two  or  three  thousandths  past 


C  A  LIFERS. 


73 


its  zero  position.  For  all  ordinary  work  the  following  method 
will  serve  well:  Adjust  the  caliper  so  the  zeroes  will  coincide 
when  the  thimble  is  turned  with  just  enough  pressure  to  raise 
the  yoke  to  a  horizontal  position.  In  calipering,  hold  the  work  in 
a  vertical  position,  and  with  the  caliper  in  the  right  hand  adjust 
the  measuring  points  onto  the  work  until  the  yoke  again  comes  up 
to  the  horizontal  position,  thus  insuring  practically  the  same  pres- 
sure between  point  and  work  as  between  point  and  anvil  when  the 
zero  setting  was  made. 

For  very  fine  work  the  application  of  the  friction  drive  to  the 
thimble  is  an  advantage.  In  Fig.  79  is  shown  a  micrometer  head 
having  such  a  device.  The  knurled  extension  contains  a  ratchet 
which,  when  the  pressure  reaches  the  desired  point,  slips.  In 


FIG.  79. 


FIG.  80. 


backing  the  screw  the  ratchet  engages  the  pawl,  making  a  positive 
drive.  The  advantage  of  the  ratchet  over  a  plain  friction  is  that 
the  screw  can  be  backed  more  rapidly  without  slipping. 

In  Fig.  80  is  shown  the  Brown  &  Sharpe  thread-measuring 
micrometer  used  for  the  accurate  measuring  of  United  States  S 
and  V  threads  on  screws,  taps,  thread  gauges,  etc.  The  end  of  the 
measuring  point  is  a  60  degree  cone  and  the  "anvil"  is  V-shaped. 
Enough  is  cut  from  the  end  of  the  measuring  point  and  the  bottom 
of  the  V  carried  sufficiently  deep  to  prevent  a  bearing  on  the  top 
or  bottom  of  the  thread  thus  giving  the  bearing  on  the  sides  of 
the  threads. 

When  the  point  and  anvil  are  together  as  shown  in  Fig.  Si, 
the  line  through  the  plane  A  B  represents  the  zero  position  and 
moving  the  measuring  point  back  any  fixed  distance  separates  by 


74 


MODERN    MACHTNE    SHOP    TOOLS. 


that  amount  the  position  of  the  plane  that  cuts  the  movable  point 
from  the  same  plane  in  the  anvil. 

As  a  sharp  V  thread  is  in  section  an  equilateral  triangle,  the 
sides  of  the  threads  are  equal  to  the  pitch  of  the  thread  and  the 
depth  of  the  thread  is  equal  to  the  side  multiplied  by  .866  =  the 
pitch  X  -866  =  .866/N  where  N  equals  the  number  of  threads 
per  inch. 

'As  the  pitch  line  is  one-half  the  depth  of  the  thread  on  each 
side,  the  pitch  diameter  is  the  whole  diameter  less  the  depth  of 
one  thread.  The  caliper  reading  is  therefore  in  any  case  the  full 
diameter  less  the  depth  of  one  thread,  which  is  determined  as 
above. 

For  the  United  States  Standard  threads  the  pitch  diameter  is 
greater  than  for  the  V  thread,  inasmuch  as  it  is  flattened  at  top  and 


FIG.  81. 


FIG.  82. 


root  an  amount  equal  to  one-eighth  of  the  pitch,  thus  making  its 
depth  one-fourth  less  than  with  the  V  threads.  In  determining  the 
caliper  reading  for  the  United  States  S  thread  the  constant  is 
three-fourths  of  .866,  or  .6495,  which  divided  by  the  number  of 
threads  and  subtracted  from  the  normal  diameter  gives  the  caliper 
reading  as  before. 

Micrometer  calipers  of  greater  capacity  than  2  inches  have 
until  recently,  been  little  used.  The  introduction  of  the  reliable, 
moderate-priced  caliper,  shown  in  Fig.  82,  has  met  a  popular 
demand  for  a  yoke  caliper  of  large  size.  It  is  a  much  more  con- 
venient tool  for  the  workman  than  fixed  caliper  gauges.  The 
yoke  section  is  a  bulbed  I,  which  gives  light  weight,  strength  and 


CALIPERS.  75 

an  excellent  grip  for  the  fingers.  All  adjustments  for  wear  are 
in  the  head.  For  the  table  of  decimal  equivalents  usually  stamped 
on  the  yoke  the  following  is  substituted :  Every  fifth  graduation 
on  the  barrel  (.125  inch)  is  extended,  and  beginning  at  the  zero 
marked  i  to  8,  inclusive,  thus  giving  an  inch  graduation  by 
eighths.  On  the  thimble  are  stamped  the  decimal  equivalents  for 
1-16  inch,  1-32  inch  and  1-64  inch,  thus  giving  a  contracted 
conversion  table,  the  application  of  which  requires  at  most  only  a 
simple  calculation,  thus,  23-32  inch  =  ^  inch  +  1-16  inch  -f- 
1-32  inch.  Set  to  the  5  and  add  the  sum  of  the  decimal  equivalents 
for  1-16  inch  (.0625  inch)  and  1-32  inch  (.0312  inch  )  =  .0937 
inch,  which  should  be  set  back  from  the  ^  in  the  ordinary  manner. 
This  does  not  interfere  with  reading  the  caliper  decimally  in  the 
ordinary  way. 

This  caliper  is  made  in  twelve  sizes,  from  i  to  12  inches.    The 


i -inch  to  6-inch  sizes  have  yokes  made  from  drop  forgings  of 
bar  steel,  and  the  larger  sizes  have  yokes  made  of  steel  castings, 
all  neatly  finished  and  japanned.  The  face  of  the  anvil  is  formed 
by  a  hardened  steel  plug  of  same  diameter  as  the  end  of  the 
measuring  point. 

The  measuring  range  of  each  size  is  i  inch,  and  for  adjustment 
of  all  sizes  other  than  the  i-inch  caliper,  standard  end  measure 
test  pieces  are  required. 

In  calipers  of  this  class  the  yoke  is  frequently  lagged  with 
wood  or  hard  rubber  to  prevent  the  expansion  and  consequent 
inaccuracies  that  arise  from  handling  with  the  warm  hand. 

A  form  of  yoke  micrometer  in  which  provisions  are  made  for 
a  wider  range  of  measurements  is  shown  in  Fig.  83.  It  is  made 
in  four  sizes  having  a  range  of  from  o  to  12  inches.  The  anvil 
is  mounted  in  the  end  of  a  spindle,  which  is  provided  with  stops 


76 


MODERN    MACHINE    SHOP   TOOLS. 


exactly  i  inch  apart.  A  slight  turn  of  the  anvil  spindle  when 
either  stop  is  to  be  used  brings  it  firmly  against  its  seat,  in  which 
position  it  is  securely  clamped. 

Beam  micrometer  calipers  are  illustrated  in  Figs.  84,  85 
and  86. 

In  each  case  the  regular  micrometer  head  of  one  inch  capacity 


FIG.  84. 


FIG.  85. 


FIG.  86. 


is  mounted  upon  a  suitable  slide  which  moves  over  the  beam  of 
the  instrument.  Three  distinct  methods,  however,  of  making  the 
several  inch  settings  are  employed. 


CALIPERS. 


77 


In  Fig.  84  the  inch  settings  are  made  to  accurately  graduated 
rulings  on  the  beam. 

In  Fig".  85  these  settings  are  made  by  inserting  the  tapered 
steel  pin  in  the  holes  in  the  sliding  jaw  and  their  corresponding 
holes  in  the  beam,  A  separate  set  of  holes  is  used  for  each  set- 
ting. The  holes  are  bushed  with  hardened  steel  bushings  ground 
and  lapped  to  fit  the  tapering  plug. 

In  Fig.  86  is  shown  a  beam  micrometer  of  six  inches  capacity. 
The  sliding  jaw  carries  a  regular  micrometer  screw  head  of  one 
inch  .range  and  moves  over  a  cylindrical  barrel  in  which  is  an 
accurately  bored  hole  to  receive  three  end  measure  test  pieces, 
one,  two  and  three  inches  long.  An  arm  on  the  head  extends  into 
the  bore  through  a  radial  slot  in  the  cylinder,  and  by  means  of 
the  test  pieces  enables  the  setting  of  the  head  at  fixed  distances 


FIG.  87. 

one  inch  apart.  A  zero  mark  on  the  cap  and  barrel  determines 
the  proper  pressure  on  the  test  pieces  for  each  setting. 

The  capacity  of  the  beam  micrometer  for  measuring  flat  work 
is  limited  only  by  the  length  of  the  beam.  For  round  work  the 
height  of  the  jaws  limits  the  diameter,  usually  to  about  4  inches, 
since  in  order  to  keep  the  weight  of  the  instrument  within  rea- 
sonable limits  it  is  not  advisable  to  make  the  jaws  much  greater 
than  2  inches  high. 

In  Fig.  87  is  shown  a  bench  micrometer  for  measuring  all 
sizes,  from  zero  to  2  inches.  It  has  a  twenty-thread  screw  with 
fifty  divisions  on  the  dividing  head,  thus  giving  direct  readings 
to  i-iooo  of  an  inch.  The  zero  adjustment  is  obtained  by  turn- 
ing the  head  on  the  screw,  it  being  held  in  position  by  a  lock 
nut.  As  a  bench  machine  its  simplicity  and  convenience  rec- 
ommend it  for  general  shop  use. 


7<5  MODERN    MACHINE    SHOP    TOOLS. 

The  Pratt  &  Whitney  standard  measuring  machine  shown  in 
Fig.  88  is  an  instrument  of  precision  for  originating  and  dupli- 
cating standard  dimensions.  It  is  a  beam  micrometer  of  the 
greatest  refinement  as  to  design  and  construction. 

The  bed  is  very  heavy  and  rests  upon  three  neutral  points  to 
overcome  flexure  and  effects  of  changes  of  temperature.  Resting 
on  the  side  of  the  bed  is  a  standard  measurement  bar  in  the 
surface  of  which  are  inserted  hardened  steel  plugs  at  intervals  of 
one  inch.  On  the  polished  surface  of  each  plug  is  a  very  fine 
ruling,  the  distance  from  ruling  to  ruling  being  one  inch  at  62 
degrees  Fahrenheit  within  a  limit  of  error  of  1-50,000  of  an  inch. 
To  one  end  of  the  bed  is  secured  a  headstock  which  carries  the 


FIG.  88. 


fixed  measuring  point.  This  point  is  secured  in  a  plunger  backed 
up  by  a  light  helical  spring.  Secured  to  the  plunger  is  an 
auxiliary  jaw  which  holds  between  its  face  and  the  face  of  another 
jaw  secured  in  the  head  a  small  cylindrical  plug  gauge  by  friction 
alone.  The  tension  of  the  spring  is  sufficient  to  hold  the  small 
gauge  at  an  angle  from  the  vertical. 

The  movable  head  carries  the  micrometer  which  consists  of  a 
5O-thread  screw  and  a  dial  having  400  divisions  with  an  adjustable 
zero  arm.  The  microscope  with  micrometer  eyepiece  is  secured 
to  the  movable  head  in  such  a  position  as  to  cause  its  line  of  sight 
to  pass  over  the  rulings  on  the  plugs  when  the  head  is  moved 
from  end  to  end  of  the  bed. 


CALIPERS.  79 

In  obtaining  the  zero  setting  the  micrometer  screw  is  run  all 
the  way  out  and  the  zero  on  the  dial  made  to  coincide  with  the  zero 
on  the  adjustable  arm.  The  measuring  points  are  next  brought 
in  contact,  approximately  by  means  of  the  fine  adjusting  screw 
shown  at  the  rear  of  the  movable  head  and  exactly  by  a  slight 
movement  of  the  micrometer  dial.  When  the  pressure  between 
the  measuring  points  is  just  sufficient  to  allow  the  "sensitive 
piece"  above  referred  to  to  drop  to  a  vertical  position  but  not  to 
fall  out,  the  zero  on  the  adjustable  arm  is  made  to  coincide  with 
the  zero  on  the  dial  and  the  hair  line  in  microscope  to  coincide 
with  the  ruling  on  the  first  plug. 

In  making  a  measurement  the  movable  head  is  carried  back 
and  the  microscope  made  to  read  on  the  ruling  on  the  plug  which 


FIG. 


corresponds  to  the  whole  number  of  inches  to  be  measured;  the 
"sensitive  piece"  is  inclined  from  the  vertical;  the  piece  to  be 
measured  is  placed  upon  the  supports  shown  and  the  measuring 
points  adjusted  against  it  with  just  the  amount  of  pressure  re- 
quired to  cause  the  "sensitive  piece''  to  swing  to  the  vertical  posi- 
tion. The  reading  is  then  taken.  The  slightest  excess  of  pressure 
will  cause  the  "sensitive  piece"  to  drop  out. 

The  direct  reading  on  the  dial  is  1-20,000  of  an  inch,  and  one- 
half  of  this  amount  can  be  quite  readily  approximated  to.  In  deal- 
ing with  such  minute  variations  in  dimensions  the  utmost  care  must 
be  observed  in  the  manipulation  and  especially  in  the  effects  of 
changes  in  temperature. 

Fig.  89  shows  the  Sweet's  measuring  machine,  which  is  made 


8o 


MODERN    MACHINE    SHOP    TOOLS 


in  4,  6  and  8  inch  sizes,  and  may  be  classed  under  the  head  of 
bench  micrometers.  This  instrument,  which  is  intended  for 
practical  shop  uses,  reads  as  regularly  furnished  to  i-iooo  and 
1-1280  of  an  inch.  When  required  a  vernier  is  used  on  the  head, 
which  gives  readings  of  1-10,000  of  an  inch.  The  range  of  meas- 
uring screw  is  i  inch,  test  pieces  being  furnished  for  setting  the 
sliding  anvil  to  the  inch  zero  positions. 

Fig.  900  shows  a  portion  of  the  measuring  head.  A  i-io  inch 
pitch  trapezoidal  thread  measuring  screw  is  employed.  This  form 
of  thread  gives  a  square  bearing  on  its  work  side,  and  the  quick 
pitch  facilitates  rapid  adjustment.  The  knurled  thumb  nut  drives 
through  a  friction.  The  outer  disc  of  the  dial  is  divided  to  hun- 


10 


FIG.  90. 

dredths,  thus  giving  for  each  division  i-ioo  of  i-io  =  i-iooo  of 
an  inch.  The  reading  is  made  on  the  front  edge  of  the  index  bar. 

For  the  fractional  readings  the  left-hand  disc  is  used.  It  is 
divided  into  128  parts,  and  every  eighth  division  numbered,  as 
shown  in  Fig.  90*7.  One  revolution  of  the  screw  equals  i-io  of 
an  inch  =  128  divisions  on  the  dial,  whence  one  division  =  i-io 
of  1-128  =  1-1280  of  an  inch.  The  upper  edge  of  the  index  bar 
is  graduated  to  sixteenths  for  convenience  in  getting  the  ap- 
proximate setting.  All  readings  are,  however,  made  on  the  front 
edge  of  the  bar. 

Referring  to  Fig.  90^  :  Following  the  straight  lines  from  o  to 
I,  2,  3,  etc.,  back  to  zero  (16)  five  complete  revolutions  are  made, 
which  carries  the  screw  back  l/2  inch.  Then  every  five  divisions 
are  5-16  of  i-io  =  1-32  of  an  inch  at  the  measuring  point,  and 


CALIPERS. 


every  2^/1  divisions  equals  1^64  of  an  inch ;  and  since  each  division 
is  divided  into  eight  equal  parts  on  the  disc,  1-128,  1-256  and 
1-1280  may  be  found  by  using  10,  5  and  i  of  these  small  divi- 
sions, respectively.  For  example,  in  Fig.  90  the  reading  line  is 
6-32  inch  beyond  the  16-32  (.5)  inch  mark  ==  22-32,  and  the  6 
on  the  disc  should  nearly  coincide  with  the  22-32  division.  Bring 
the  6  to  read  at  the  lower  edge,  and  the  measuring  point  will  be 
22-32  inch  from  the  anvil.  If  23-32  inch  had  been  wanted,  the  7 
on  the  disc  would  have  been  brought  around  to  the  reading  edge. 
If  47-64  inch  was  required,  the  7  would  be  carried  past  the  read- 
ing edge  twenty  divisions  and  in  like  manner  ten  more  divisions 
would  make  it  read  95-128  inch. 

Any  error  in  the  pitch  of  the  measuring  screw  which  would 


FIG.  91. 

affect  the  number  of  turns  per  inch  is  corrected  by  setting  the 
index  bar  at  an  angle  with  the  axis  of  the  screw.  Assume,  for 
example,  that  the  ten  turns  of  the  screw  advance  the  measur- 
ing point  i-iooo  inch  too  far.  The  screw  is  too  long,  and  less 
than  ten  revolutions  should  be  made  by  an  amount  equal  to  one 
of  the  divisions  on  the  outer  disc.  The  outer  end  of  the  index 
finger  will  be  raised  this  amount  above  the  inner  end  gradua- 
tion. This  corrects  the  error  proportionately  from  end  to  end  of 
the  screw. 

An  example  of  the  inside  micrometer  caliper  is  shown  in 
Fig.  91.  It  is  used  for  making  inside  measurements  and  reads 
to  thousandths  through  a  ^<-inch  range.  The  instrument  shown 
with  its  extension  rods  makes  any  measurement  between  3  and  6 
inches.  The  nut  and  check  nut  on  the  extension  rods  may  be 
adjusted  down  to  compensate  for  any  wear  of  the  points. 


CHAPTER  VI. 


GAUGES  AND  INDICATORS. 

There  is  nothing  more  confusing  to  the  young  mechanic  than 
the  use  of  the  several  systems  of  gauges  used  in  designating 
the  sizes  of  wire,  machine  screws,  drills  and  plate  thicknesses. 
Unfortunately,  most  of  these  dimensions  differ  from  each  •  other 
for  corresponding  numbers  by  comparatively  small  amounts,  yet 
an  amount  sufficient  to  cause  error  if  the  one  is  mistaken  for 
the  other.  The  following  table  gives  for  comparison  values  for 
only  a  few  numbers  under  each  of  the  several  gauges  in  most 
common  use : 


• 

fli       " 

V 

QJ 

U.      V-«      -. 

QJ 

"^3  oJ 

£3 

<U           ttJ 

0  8?. 

c  « 

"*""  'd  tJ5 

•r<     bJO 

.~   &c 

o 

G    ^         rt 

^J?t> 

?  3 

SO 

•2i  a 

Q  oJ 

^      CJO 

2    i-    3 

313 

II 

1p 

"S 

'1  8  & 

^e^o 

g  ^ 

rO    <y 

50 

W     rt     4J 

1J5 

-o1^  ^ 

fi        <u 

0* 

£   "     JH 

c  '5  ^ 

t—  I    ^ 

^_,     «^H 

C/2 

'S  ^  JS 

r/^  ^ 

5            0 

25 

<      c/) 

w     w 

^ 

p        PH 

'72        C/3 

i 

.2893 

.3 

3 

.227 

.228 

.28125 

.0156 

.071 

5 

.1819 

.22 

.212 

.204 

2055 

.2187; 

.0202 

.124 

10 

.10189 

•134 

.128 

.191 

•1935 

.I4C62 

.027 

.189 

15 

.05707 

.072 

.072 

.178 

.18 

.07031 

.0345 

•255 

20 

.03196 

•035 

•035 

.161 

.161 

•0375 

.0434 

.321 

The  dimensions  are  purely  arbitrary.  The  American,  or 
Brown  &  Sharpe  gauge,  was  brought  out  in  the  production  of  a 
gauge  to  overcome  the  irregularities  in  spacing  of  the  Birmingham 
wire  gauge.  In  this  gauge  the  dimensions  increase  by  a  regular 
geometrical  progression.  The  largest  dimension  is  No.  oooo, 
which  equals  .46  of  an  inch.  The  next  smaller  number,  ooo,  is 
obtained  by  multiplying  .46  by  the  constant  .890522.  This  pro- 
duct again  multiplied  by  the  same  constant,  gives  the  next  smaller 
number,  and  in  like  manner  each  number  is  the  product  of  the 
preceding  number  and  this  constant.  A  comparison  of  the  Eng- 
lish and  American  gauges  is  best  shown  in  Fig.  92,  where  the 
peculiar  irregularities  of  the  former  are  plainly  shown. 

The  Imperial  wire  gauge  differs  but  little  from  the  English.  It 
was  adopted  by  the  English  Board  of  Trade  in  1884  as  a  substi- 
tute for  the  Birmingham  gauge.  The  Stubs'  steel  wire  gauge 


GAUGES   AND   INDICATORS.  83 

differs  materially  from  those  above  cited.  Its  range  carries  it 
from  No.  I  to  No.  80,  variations  in  dimensions  being  indicated 
to  the  nearest  thousandths  of  an  inch.  The  difference  be- 
tween consecutive  numbers  differs  in  dimensions  from  one  to  at 


c. 


-19 


_20 


27- 


FIG.  92. 


FIG.  93. 


most  only  a   few  thousandths,   the   eighty   numbers   carrying  it 
through  but  .214  of  an  inch. 

It  is  extremely  unfortunate  that  a  single  standard  gauge  could 
not  be  adopted  and  used  to  the  exclusion  of  all  others,  at  least 
in  our  own  country,  and  thereby  avoid  all  the  confusion  incident 
to  the  promiscuous  use  of  the  several  so-called  standards.  Even 


84  MODERN    MACHINE    SHOP    TOOLS. 

the  manufacturers  of  brass  and  copper  stock,  who  have  adopted 
the  American  standard,  do  not  confine  themselves  exclusively 
to  this  gauge,  as  much  of  their  product  is  still  gauged  by  the 
English  system. 

The  Stubs'  drill  gauge  varies  from  the  Stubs'  steel  wire  gauge 
by  from  o  to  3  thousandths  of  an  inch  oversize,  which  is  simply 
the  average  oversize,  determined  by  a  great  number  of  measure- 
ments, of  wire  drawn  through  Stubs'  wire  gauge  dies,  and  might 
be  compared  with  a  maximum  limit  gauge,  as  the  dies,  when 
worn  to  such  an  extent  as  to  produce  wire  over  the  sizes  indi- 
cated by  the  drill  gauge,  are  replaced  by  new  ones. 

It  will  be  noted  that  as  the  designating  number  of  the  gauge 
increases,  the  dimensions  decrease  for  all  except  the  steel  music 
wire  and  machine  screw  gauges,  which  increase  in  diameter  as 
the  number  increases.  This  also  tends  .much  toward  confusion, 
and  may  be  looked  upon  as  another  anomaly  of  the  present 
gauge  systems. 

The  gauges,  or  tools  for  indicating  the  gauge  of  wire  or  plates, 
are  of  two  forms,  the  angular  and  the  notch.  The  angular  gauge 
is  shown  in  Fig.  93.  With  this  tool  the  measurement  is  made 
by  passing  the  screw,  wire  or  plate  into  the  angular  opening 
until  it  touches  both  sides;  the  reading  opposite  the  point  of  con- 
tact giving  the  gauge  of  the  material.  When  used  for  gauging 
plates,  this  gauge  should  be  made  with  open  end,  as  shown  at 
C.  On  the  one  side  is  graduated  the  English  and  American 
standards,  and  on  the  other  the  machine  screw  gauge  and  parts 
of  an  inch.  The  notch  gauge  is  shown  at  A  in  Fig.  94.  In  using 
this  tool  the  article  measured  should  just  pass  through  one  of  the 
slots,  the  number  opposite  indicating  the  gauge.  These  gauges 
may  be  had  with  the  decimal  equivalent  of  each  size  stamped  on 
the  back  of  the  tool,  which  will  frequently  IDC  found  a  great 
convenience.  Another  form  of  notch  gauge  is  shown  at  B  in 
Fig.  94.  This  is  called  a  rolling  mill  gauge,  and  is  used  for 
gauging  sheet  metals.  They  may  be  had  either  in  the  English  or 
United  States  standard  plate  gauges. 

As  there  is  considerable  wear  upon  gauges  of  this  class,  and 
especially  those  of  the  notch  pattern,  it  is  important  that  they 
should  be  made  of  good  steel,  carefully  hardened  and  tempered. 
In  order  that  tools  of  this  character  can  be  put  upon  the  market 
at  a  reasonably  low  price,  high  accuracy  requirements  in  their 
manufacture  cannot  be  attempted.  For  all  ordinary  gauging  they 


GAUGES    A XI)    INDICATORS.  85 

be  found  sufficiently  accurate,  and  when  greater  exactness 
is  demanded  the  micrometer  caiiper  should  be  used,  the  decimal 
equivalent  of  the  gauge  required  being  taken  from  a  table  on  the 
back  of  the  gauge. 

In  Fig.  95  is  shown  a  drill  gauge.  Stubs'  drill  sizes,  from  Xo. 
i  to  Xo.  60.  A  smaller  size  with  holes  from  Xo.  61  to  80,  is 
made.  It  may  also  be  had  with  holes  from  1-16  to  ^  inch,  vary- 
ing by  64ths,  the  latter  being  known  as  the  "jobbers' "  drill 


B. 


FIG.  94. 


gauge.     As  it  is  not  practical  to  attempt  to  stamp  the  sizes  on 
very  small  drills,  these  gauges  are  quite  necessary. 

The  nut  and  washer  gauge  shown  in  Fig.  96  is  so  graduated 
as  to  show  readily  the  diameter  of  holes  within  its  capacity.  A 
very  convenient  feature  in  this  gauge  is  the  dimensions  giving 
sizes  of  holes  to  tap  United  States  standard  threads.  A  gauge 
of  this  kind  will  be  found  excellent  for  measuring  small  holes 
or  narrow  slots,  which  are  too  small  to  be  calipered,  and  fre- 
quently in  inaccessible  places  where  they  cannot  be  scaled. 


86 


MODERN    MACHINE    SHOP    TOOLS. 


In  Fig.  97  is  shown  a  center  gauge,  which,  as  its  name  indi- 
cates, is  used  for  gauging  lathe  and  other  machine  centers,  in 
turning  or  grinding  them.  It  may  also  be  used  as  a  gauge  for 


ilO  D:O  O  C  O  O  O  O  O  O  O:4 

'  a  13       14       15        16        17       18       19       20      2,1       22      23       24      25    " 

E-C  CXsD    O   O   D   O   O  O    C   O   O  C 

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4O    O  "=Q   O    O   O    O    O  O    C^    O-  o    o   o    o   ov 

-£42    43    44-45    46   47    48  49-  50- ,51  =52    53  :54- S_5- 56^-5:7  58^59^60 

^  C       O       O        Q        C        f        f>       &       e        r>       f,        x        *....... 

; 


FIG.  05. 


FIG.  96. 


,\    ,\    ,\    ,\    ,\    A    A    A    A 


CENTRE    GAUGE, 

AND 

GAUGE    FOR    GRINDING 
AND   SETTING  SCREW  TOOLS, 


FIG.  97. 


grinding  and  setting  threading  tools,  a  number  of  its  uses  in  this 
connection  being  clearly  shown  in  this  figure.  The  angles  are  60 
degrees,  and  the  table  of  equivalents  shown  is  to  determine  the 


GAUGES   AND  INDICATORS.  87 

proper  diameter  of  hole  for  tapping  full  V  threads.  In  this  table 
the  numbers  in  the  first  and  third  columns  are  threads  per  inch, 
and  those  in  the  second  and  fourth  columns  the  double  depth  of 
V  threads  of  the  corresponding  pitches.  Thus  the  tap  drill  for 


FIG.  98. 

a  24  tap,  K)  threads  per  inch',  would  be  .75  —  .173  =  .577  =  37-64 
inch. 

The  screw  thread  gauge  is  shown  in  Fig.  98.     The  one  60 


PIG.  99. 

degree  V  notch  will  gauge  all  V  threads;  the  others,  however, 
are  flattened  at  the  root  by  the  amount  the  top  of  the  thread  is 
cut  off  in  the  various  pitches  of  the  United  States  standard 


88 


MODERN    MACHINE    SHOP    TOOLS. 


thread.  These  gauges  are  for  use  in  grinding  threading  tools, 
and  may  be  had  for  worm,  Whitworth  and  "Acme  standard" 
threads. 

The  screw  pitch  gauge,  Fig.  99,  has  a  large  number  of  thin 
blades,  which  fold  up  into  a  suitable  handle.  Each  blade  has 
two  or  more  teeth,  of  the  pitch  corresponding  to  that  stamped 
on  the  blade.  By  direct  comparison  with  a  screw  thread  the 
exact  pitch  may  be  determined  without  the  danger  of  errors 
that  arises  when  the  threads  are  counted  over  the  edge  of  a  rule. 
The  decimal  following  the  pitch  number  on  each  blade  is  the 
double  depth  of  the  thread.  The  thickness  gauge,  shown  in  Fig. 
100,  consists  of  a  number  of  thin  steel  leaves,  varying  by  thou- 


THE  J..S.S  TA ;  R  R  £  T  T_  C  O . 
'  ATH'O L .  MAS 5    U  S.A 


FIG.    100. 


FIG.    102. 


FIG.    101. 


sandths  in  thickness.  The  leaves  may  be  used  singly  or  together, 
thus  making  any  thickness  desired  within  the  limits  of  the  tool. 
The  value  of  a  tool  of  this  kind  can  only  be  learned  by  having  one 
in  the  vest  pocket,  where  its  convenience  to  hand  will  find  many 
chances  for  its  use. 


GAUGES    AND    INDICATORS.  89 

The  depth  gauge,  an  example  of  which  is  shown  in  Fig.  10.1, 
is  used  for  measuring  the  depth  of  holes  or  recesses.  The  blade 
should  be  narrow,  and  for  general  work  graduated  on  one  edge 
to  64ths  and  on  the  other  to  looths.  The  beam  or  head,  when  six 
inches  long,  will  meet  most  general  requirements.  This  tool  will 
be  most  highly  appreciated  by  the  man  wrho  has  often  attempted 
to  measure  carefully  the  exact  depth  of  a  recess  by  holding  two 


FIG.   103. 

slippery  steel  rules  at  right  angles  to  each  other  between  his 
thumb  and  fingers,  and  attempted  to  read  the  one  over  the  edge 
of  the  other.  For  very  accurate  depth  measurements  these  gauges 
are  made  in  a  micrometer  pattern,  which  is  graduated  to  read 
directly  to  thousandths. 

While  on  the  subject  of  gauges  we  should  not  overlook  the 
simple  yet  useful  one  shown  in  Fig.  102.  The  scratch  gauge  con- 
sists of  an  arm,  preferably  graduated,  carrying  a  sliding  guide, 
which  can  be  clamped  at  any  position  on  the  arm,  and  provided 


90  MODERN    MACHINE    SHOP    TOOLS. 

with  a  short,  hard  and  sharp  scriber  at  the  end.  This  tool  is  used 
in  ruling  lines  parallel  with  the  edge  of  work. 

In  Fig.  103  is  shown  one  of  the  many  types  of  surface  gauges. 
Although  this  tool  comes  last  in  the  long  list  of  useful  gauges 
above  illustrated,  it  is  by  no  means  the  least  important,  as  the 
machinist  undoubtedly  uses  it  more  in  general  machine  shop 
operations  than  all  the  others  combined.  The  principal'  use  of 
this  tool  is  in  determining  the  parallelism  of  one  plane  with  an- 
other, usually  the  surface  of  the  work  with  the  machine  table, 
housing,  cross-rail  or  other  reference  planes.  In  testing,  erect- 
ing and  setting  up  work  on  machine  tools  the  surface  gauge  is 
indispensable. 

The  simpler  the  gauge  is  made  the  better  it  is,  as  numerous 


FIG.  104. 

tricks  and  devices  on  a  tool  of  this  kind  usually  complicate  and 
decrease  rather  than  increase  its  value.  In  setting  the  point  of  the 
needle  to  a  line  or  point  the  clamping  screw  should  be  so  adjusted 
that  the  needle  moves  smoothly  yet  with  considerable  friction. 
The  power  applied  to  the  needle  to  turn  it  should  be  on  the 
opposite  side  of  the  fulcrum  from  the  work,  as  in  that  case  the 
spring  of  the  needle  is  outside  of  the  fulcrum  and  the  point  stays 
where  placed.  If  the  force  is  applied  inside  the  fulcrum  the 
spring  will  make  it  difficult  to  set  the  point  as  desired.  When,  as 
with  the  gauge  shown,  a  screw  adjustment  is  provided,  the  exact 
setting  is  made  with  this  adjustment. 


GAUGES   AND   INDICATORS.  9 1 

In  Fig.  104  is  shown  a  form  of  adjustable  limit  gauge. 
When  used  as  a  limit  gauge  the  outer  screw  is  adjusted 
to  the  maximum  allowable  dimension  and  the  inner  screw  to 
the  smallest  allowable  dimension.  The  work  to  pass  inspection 
must  pass  through  the  outer  gauge  and  not  through  the  inner. 
This  tool  when  used  as  a  snap  gauge  is  provided  with  but  one 
screw.  It  is  customary  to  set  the  gauge  on  a  plug  or  other 
standard  and  by  means  of  the  jamb  nut,  lock  the  screw  in  posi- 
tion. The  screws  and  anvils  are  hardened  and  ground. 

A  test  indicator  is  a  tool  used  in  determining  small  variations 
from  the  true  rotation  of  a  cylindrical  surface  and  irregularities 
or  inaccuracies  in  its  cylindrical  truth.  It  can  also  be  used  in 
determining  the  inaccuracies  of  a  plane  surface,  and  small 


FIG.  105. 

amounts  of  end  or  lateral  motion,  as  for  example,  the  end  motion 
of  a  spindle  or  the  deflection,  give  or  wink  between  gibbed  sur- 
faces, etc.  These  tools  are  of  two  types ;  those  which  simply  in- 
dicate, and  those  which  give  a  reading  that  shows  the  exact 
amount  of  the  error  or  untruth.  In  Fig.  105  is  shown  an  instru- 
ment of  the  latter  class.  The  adjustments  of  this  tool  are  quite 
evident  from  the  figure.  The  long  pointer,  the  one  end  of  which 
moves  over  a  graduated  arc  with  readings  to  one  one-thousandth 
of  an  inch,  as  fulcrumed,  bears  the  hardened  point,  which  comes 


Q2  MODERN    MACHINE    SHOP    TOOLS. 

in  contact  with  the  surface  to  be  tested.  The  reading  is  magni- 
fied by  the  long  pointer,  and  the  zero  of  the  scale  is  at  the  cen- 
ter of  the  arc,  which  reads  ten-thousandths  of  an  inch  each  side 
of  this  point.  A  light  spring,  secured  to  the  pointer,  and  held 
between  adjusting  screws  near  the  pivot,  provides  for  the  con- 
venient adjustment  of  the  pointer  to  the  zero  reading,  no  matter 
what  the  position  of  the  arm. 

Instruments  of  this  character  must  be  carefully  made,  and  are 
of  great  value  in  the  erection  and  testing  of  accurate  machinery. 
When,  however,  only  an  indication  of  untruth  is  required,  as  in 
the  chucking,  centering  or  setting  up  of  work,  a  much  cheaper  tool 
serves  the  purpose,  as  for  example,  the  one  shown  in  Fig.  106.  In 
this  tool  the  pointer  is  held  in  a  universal  socket,  which  is  carried 
on  the  end  of  a  bar  of  suitable  form  to  clamp  in  the  tool  post 
of  the  lathe.  If  the  point  is  brought  against  the  rotating  work, 
the  amount  of  motion  at  the  outer  end  of  the  pointer  indicates 


FIG.  106. 

the  extent  to  which  the  work  is  out  and  the  way  in  which  to  move 
it  in  truing.  It  is  a  superior  method  of  truing  nice  work,  which 
will  not  injure  its  surface,  as  is  so  apt  to  be  the  case  when  trued 
to  the  point  of  a  lathe  tool. 

One  of  the  neat  applications  of  this  tool  is  in  the  centering  of 
a  piece  of  work,  in  the  chuck  or  against  the  face  plate,  to  a  point. 
The  sharp  end  of  the  indicator  pointer  is  set  in  the  point  to  be 
centered,  and  the  work  revolved.  This  causes  the  outer  end  of 
the  pointer  to  describe  a  circle,  the  diameter  of  which  deter- 
mines how  much  the  point  is  out  of  center.  By  properly  set- 
ting the  instrument  this  circle  will  be  described .  around  the  tail 
center,  and  when  the  work  is  exactly  centered  the  pointer  re- 
mains stationary  in  front  of  the  tail  center. 

The  above  serve  to  illustrate  a  few  of  the  many  applications 
of  an  exceedingly  satisfactory,  yet  not  extensively  used,  class  of 
test  tools. 


CHAPTER    VII. 

RULES,    SQUARES    AND    OTHER    SMALL    TOOLS 

No  tool  in  the  machinist's  kit  is  more  often  referred  to  than 
the  steel  rule.  Upon  it  he  depends  in  making  all  ordinary  meas- 
urements and  for  the  setting  of  his  calipers  and  dividers.  In 
Fig.  107  is  shown  a  standard  steel  rule  or  scale.  They  are  made 
in  various  lengths,  from  one  to  forty-eight  inches,  with  any  de- 
sired gradation,  not  exceeding  i-ioo  of  an  inch  in  fineness.  For 
shop  work  the  graduation  most  used  is  eighths,  sixteenths,  thirty- 
seconds  and  sixty-fourths,  on  the  four  corners  of  the  scale.  A 
scale  graduated  sixteenths,  thirty-seconds,  sixty-fourths  and  one- 
hundredths  is  convenient,  as  the  looth  graduations  will  serve 
for  measurements  when  required  in  decimals.  Where  all  the 
work  is  measured  bv  fractions,  however,  the  former  is  the  safest 


I 


M 


ATHLMASS.US.A. 


• '  mi 


28 

niinffiiii 


FIG.   lO/. 

ruling  to  use,  as  there  is  then  no  danger  of  inadvertently  mis- 
taking a  tenth  for  an  eighth  division,  etc.  For  this  reason,  rules 
graduated  in  twelfths  and  fourteenths  should  not  find  their  way 
into  the  machinist's  tool  box,  as  he  will  not  have  occasion  to 
use  these  divisions,  and  their  presence  will  call  for  greater  care 
in  selecting  the  proper  division,  with  the  loss  of  time  incident  to 
changing  ends  with  and  turning  over  the  rule  in  order  to  get 
at  the  division  required.  The  end  graduation,  as  shown  in  Fig. 
1 08,  is  frequently  very  convenient  in  taking  measurements  in  re- 
cesses where  the  length  of  the  scale  would  prevent  the  use  of  the 
regular  graduation. 

Standard  steel  rules,  as  made  by  our  leading  makers,  are  re- 
markably accurate.  To  be  sure,  the  length  varies  slightly  with 
the  changes  in  temperature,  but  these  changes  are  not  ordinarily 
great,  and  the  material  measured  is  usually  affected  about  the 


94 


MODERN    MACHINE    SHOP    TOOLS. 


same  amount  in  the  same  direction ;  so  we  may  feel  assured  that 
any  errors  arising  from  this  source  are  well  within  the  limit  of 
the  personal  error  of  the  operator  in  making  a  measurement. 

The  late  refinements  in  the  manufacture  of  steel  rules  have 
enabled  the  production  of  very  accurate  tempered  ones  on  com- 
paratively thin  steel.  What  we  usually  know  as  the  standard 
rule,  however,  is  graduated  on  thick  steel,  and  is  not  tempered. 
The  tempered  rules  possess  the  decided  advantage  of  resistance 
to  wear.  An  untempered  rule  is  easily  mutilated,  and  soon 
rounds  its  corners  through  wear,  making  its  ends  unfit  for  ref- 
erence. The  tempered  rules  may  be  classed  as  heavy,  tempered, 
semi-flexible  and  flexible.  The  heavy  are  about  one-tenth ;  the 
tempered,  one-twentieth ;  the  semi-flexible,  one-fortieth,  and  the 
flexible  one-eightieth  of  an  inch  thick.  For  general  work  the 
heavy  or  tempered  will  be  found  best  suited.  The  flexible  are 


=^"g> 

T  i 

i 

iTi 

1  i  i 
iiilih 

'   '  I  •  L'l 
HI  HI  Ii  in  HI 

FIG 

108. 

in  i    nun  i  ii  1  1' 

21 

10 

14 

1  1  M  LI  M  111  I 

in    1  1  1  M  1  1  1  1  1  1  1 

20 

ia 

1  1  1  |  1  1  1  M  |  1 

in     1  1  1  ii  1  1  II  il 

19 

12 

1  1  M  1  1   1  M  1 

1  1  1     iililLLLLJ 

18 

11 

MINIMI 

M      1  II  |  1  1  1  1  1  1 

17 

10 

1   1  1   1  |   1   1  1 

II      1  1  1  1  1  1  1  1  1  1 

10 

9 

1    1    1    1   1    1    | 

i  1       1  l  1  1  1  1  1  1  1  1 

15 

2                            8 

1    1    1    1    1    1 

FIG.  109. 

graduated  on  one  side  only,  and  are  of  value  in  measuring  curved 
or  irregular  outlines. 

In  this  connection  it  will  be  well  to  call  attention  to  the  gear 
rule  shown  in  Fig.  109.  Its  application  is  in  the  sizing  of  gear 
blanks  and  where,  by  rule  of  thumb,  two  diametrical  pitches  are 
added  to  the  pitch  diameter  of  the  gear  in  obtaining  the  whole 
diameter.  Thus,  if  the  pitch  is  No.  7  diametrical  and  the  num- 
ber of  teeth  34,  then  the  pitch  diameter  =  34-7  =  4  6-7  inches, 
and  the  blank  or  whole  diameter  —  4  6-7  +  2~7  =  5  l~7  inches, 
which  can  be  taken  directly  from  the  scale.  This  rule  is  of  great 
convenience  where  many  blanks  for  varying  pitches  and  num- 
bers of  teeth  are  to  be  sized. 

In  Fig.  no  is  shown  a  neat  kink  which  will  be  found  of  value 
in  taking  measurements  similar  to  the  ones  shown  in  the  figure, 
as  well  as  for  setting  inside  calipers.  The  hook  may  be  quickly 
removed.  It  is  hardened,  and  in  connection  with  a  tempered 
rule  forms  a  reliable  tool. 

In  Fig.  in  is  shown  a  standard  steel  square.     This  tool  is 


RULES,    SQUARES    AND   OTHER    SMALL    TOOLS. 


95 


made  of  cast  steel,  tempered  and  accurately  finished.  The  two 
sides  of  the  angle  are  called  the  blade  and  the  beam,  the  length 
of  the  blade  being  measured  from  the  inside  of  the  beam.  The 
form  shown  in  Fig.  112  is  preferable  when  the  length  of  the 
blade  exceeds  eighteen  inches,  as  it  can  be  more  readily  repaired 
in  case  of  accident. 

Either  of  the  methods  shown  in  Figs.  113  and  114  may  be  used 
by  the  machinist  in  testing  the  accuracy  of  a  square,  the  latter 
being  the  more  exact  of  the  two.  In  Fig.  113  A  is  a  plane  plate 


PIG.  TI 2. 


r* 

£ 

*  r 

B  , 

D 

C 

[     F'  1 

!          G        1 

PI 

G.  113. 

FIG.  114. 


of  iron  with  one  edge,  B  C,  perfectly  straight.  The  surface  A 
should  be  smooth  and  true.  The  square  is  first  applied  as  shown 
at  F  and  a  fine  line  D  E  scribed  along  its  edge.  It  is  then  re- 
versed to  position  G,  when,  if  the  edge  exactly  lines  with  the 
ruling  D  E,  the  square  is  correct.  If,  however,  the  edge  and  line 
do  not  coincide,  the  square  is  inaccurate  by  one-half  the  varia- 
tion as  shown.  Since  this  method  depends  for  its  accuracy  on 
the  eye  of  the  operator  it  cannot  be  called  an  exact  one.  The 
method  shown  in  Fig.  114  reduces  the  amount  of  the  personal 
error,  since  the  eye  detects  readily  the  ray  of  light  that  passes 
through  an  exceedingly  small  opening.  In  the  figure  the  cylin- 


96 


MODERN    MACHINE    SHOP    TOOLS. 


der  A,  which  has  been  ground  accurately  parallel  and  faced  on 
the  lower  end  slightly  dishing,  rests  on  a  plane  surface,  a  stand- 
ard surface  plate  being  best  suited  to  this  purpose.  As  the  sur- 
face of  the  cylinder  is  at  right  angles  to  the  surface  of  the  plate 
the  square  can  be  compared  with  this  angle  by  placing  it  as 
shown  in  the  figure. 

For  most  general  work  the  thin  steel  squares  shown  in  Fig. 


FIG.   115. 

115  serve  very  well.  They  are  cut  from  sheet  steel,  carefully 
made  but  not  hardened,  and  are  usually  graduated,  as  shown,  on 
both  sides. 

The  combination  square  shown  in  Fig.   116  is  a  satisfactory 


FIG.    Il6. 


tool,  which,  with  careful  use,  retains  its  accuracy.  The  blade  is 
readily  adjusted  to  any  required  length,  which  is  of  special  value 
in  transferring  measurements.  The  45  degree  angle  is  of  fre- 
quent value,  as  is  the  centering  head  which  is  used  on  the  blade 


RULES,    SQUARES    AND   OTHER    SMALL   TOOLS. 


97 


as  shown.  The  blade  is  a  standard  steel  rule,  splined  to  receive 
the  key  which  draws  the  edge  of  the  blade  close  to  its  seat  in 
the  beam. 

In  Fig.  117  is  shown  a  box  square,  or  as  it  is  more  commonly 
known,  a  key  seat  rule.  With  this  tool  lines  upon  a  cylindrical 
surface  parallel  with  the  axis  may  be  drawn.  While  it  is  in- 
tended for  use  on  external  surfaces,  as  shown  at  A,  Fig.  118,  it 
will  at  times  serve  a  good  purpose  on  internal,  as  shown  at  B, 


FIG.  117. 


FIGS.  118  AND  119. 


same  figure.  A  form  of  box  square,  shown  in  section  in  Fig. 
119,  possesses  the  advantage  of  wider  range  than  that  of  Fig.  117. 

In  Fig.  1 20  is  shown  a  pair  of  key  rule  blocks  attached  to  a 
common  steel  rule  thus  making  a  very  simple  and  efficient  key 
seat  rule. 

For  a  great  deal  of  his  work  the  machinist  is  satisfied  with 
using  the  edge  of  a  good  steel  rule  to  determine  its  straightness ; 
but  when  he  wants  to  know  to  a  certainty  that  the  work  is 
straight  it  is  a  source  of  great  satisfaction  to  be  able  to  refer  to  a 
standard  straight  edge  Such  a  straight  edge  is  shown  in  Fig. 
121.  It  is  a  piece  of  steel  of  thickness  depending  on  its  length, 
nicely  finished,  with  its  two  edges  parallel  with  each  other  and 


MODERN    MACHINE    SHOP    TOOLS. 


straight.     They  are  regularly  made  up  to  six  feet  in  length,  such 
a  tool  being  about  three  inches  wide  by  three-eighths  of  an  inch 


FIG.  1 20. 


thick.    Up  to  four  feet  in  length  they  are  frequently  tempered  on 
the  edges. 

A  cast  iron  or  surface  straight  edge  is  shown  in  Fig.   122. 


FIG.  121. 


These  tools  are  designed  for  an  entirely  different  class  of  work 
than  the  one  shown  in  Fig.  121.  The  edge  is  wide  and  scraped 
to  a  true  plane,  with  the  body  so  formed  as  to  best  resist  defiec- 


FIG.    122. 


tion  from  its  own  weight  and  distortion  due  to  changes  in  tem- 
perature. These  straight  edges  are  used  in  the  production  of 
long  plane  surfaces  like  planer  bed  V's  and  lathe  shears,  pre- 


RULES,    SQUARES    AND   OTHER    SMALL   TOOLS. 


99 


cisely  as  the  surface  plate  is  used  in  the  production  of  broad 
plane  surfaces,  and  they  are  generally  much  larger  and  heavier 
than  the  style  shown  in  Fig.  121. 

Hack  saws  are  used  for  severing  purposes,  both  by  hand  and 
power,  the  comparatively  recent  introduction  of  the  power 
hack  saw  machine  having  increased  many  times  the  possible  use- 
fulness of  the  hack  saw  blade,  a  cut  of  which  is  shown  in  a  hand 
frame  in  Fig.  123.  The  original  Stubs'  and  German  blades  were 
soft  enough  to  be  sharpened  by  riling,  were  made  of  excellent 
material,  and  were  high  in  price.  Their  expense  and  the  trouble 
required  to  keep  them  properly  sharpened  limited  their  use  to  a 
narrow  range.  The  bringing  out  of  the  modern  hard  blade,  at  a 
price  sufficiently  low  to  warrant  throwing  it  away  as  soon  as  it 
became  too  dull  to  do  satisfactory  work,  has  practically  super- 


FIGS.   123  AND  124. 


seded  the  old  blade  and  made  the  hack  saw  one  of  the  most 
important  tools  in  the  machinist's  kit. 

Hack  saw  blades  are  made  with  fourteen  teeth  per  inch  for 
general  work.  When,  however,  they  are  to  be  used  on  tubing 
or  thin  metal  a  greater  number  of  teeth  is  advisable,  as  they 
will  not  bite  so  freely,  and  the  danger  of  stripping  the  teeth  is 
much  less.  For  this  purpose  blades  having  twenty-five  teeth 
per  inch  may  be  had. 

As  with  a  file,  the  fineness  of  the  bite  depends  on  the  number 
of  teeth  in  contact  with  the  work.  The  judgment  of  the  operator 
must,  therefore,  determine  what  pressure  to  apply  on  the  saw 
for  the  varying  conditions  of  cut.  As  with  other  cutting  tools,  the 
hack  saw  does  more  work  and  stands  up  to  it  better  when  the 


IOO  MODERN    MACHINE    SHOP    TOOLS. 

pressure  is  sufficient  to  make  the  teeth  cut  free,  rather  than 
scrape  and  glaze  the  surface,  as  is  the  result  when  the  pressure 
is  too  light.  The  blade  must  be  strained  in  the  frame  to  prevent 
its  kinking.  The  strokes  should  be  uniform,  not  exceeding  forty 
per  minute.  Oil  should  not  be  used  on  the  teeth,  as  it  decreases 
their  cutting  efficiency.  Blades  are  regularly  made  from  six  to 
eighteen  inches  long,  those  exceeding  twelve  inches  being  little 
used.  For  any  work  the  blade  should  be  as  short  as  possible,  as 
the  cost  of  the  blade  and  danger  of  breakage  increases  with  its 
length.  Blades  longer  than  eight  inches  for  hand  and  twelve 
inches  for  power  frames  are  seldom  required.  The  frame  should 
be  stiff.  In  this  respect  the  non-adjustable,  or  solid  one,  shown 
in  Fig.  124,  is  preferable.  All  hand  frames  should  be  so  con- 
structed that  the  blade  can  be  faced  at  right  angles  to  the  posi- 
tion shown  in  the  figure,  which  is  quite  necessary  when  a  deep 
cut  is  to  be  taken  near  the  edge  of  the  work. 

Everybody  uses  the  screw  driver,  yet  how  seldom,  even  among 
mechanics,  do  we  find  it  properly  ground.  In  Fig.  125  is  shown 

at  A  an  edge  view  of  the  point  of 
a  screw  driver,  as  usually  ground ; 
and  at  B  a  view  showing  how  it 
should  be  ground.  When  the 
screw  driver,  A,  is  applied  to  the 
slot  of  the  screw  head  it  bears  only 
at  the  center  of  the  upper  edges, 
C  and  D,  of  the  slot,  and  the  force 
required  to  turn  the  screw  forces 
the  driver  out  of  the  slot,  which 

FIG.  125.  injures,  if  not  completely  ruins,  the 

head   of   the   screw.     With    B    the 

case  is  different.  The  parallel  sides  of  the  bit  take  squarely 
a  hold  of  the  sides  of  the  slot  and  the  screw  is  driven  without  in- 
jury, and  with  much  less  exertion  than  in  the  former  case.  The 
screw  driver  should  be  made  of  good  tool  steel  and  given  a  tough 
temper. 

In  Fig.  126  is  shown  that  much  used  tool,  the  monkey  wrench. 
This  is  a  genuine  wrench,  and  should  only  be  used  as  such.  It 
should  never  be  used  as  a  hammer ;  neither  should  it  be  expected 
to  stand  all  the  force  a  thoughtless  workman  can  apply  at  the  end 
of  four  feet  of  gas  pipe  slipped  over  the  handle  as  an  extension. 
It  should,  however,  when  properly  closed  on  the  flats  of  a  nut, 


RULES,    SQUARES    AND   OTHER    SMALL   TOOLS. 


101 


stand  safely  all  the  average  man  would  care  to  exert  with  both 
hands  on  the  handle.  As  the  nut  often  starts  more  easily  with  a 
quick  jar  or  shock  than  by  the  application  of  a  steady  force,  it 
is  permissible  to  strike  the  end  of  the  handle  in  the  direction 
shown  by  the  arrow  with  a  rawhide  or  wooden  mallet,  or  the 
end  of  a  soft  block  of  wood.  The  operator's  judgment  must 
determine  how  heavy  a  blow  he  can  safely  use. 

The  surfaces  A  B  should  be  smooth,  plane,  and  parallel  with 
^ach  other.  These  wrenches  usually  fail  by  bending  at  C.  If 
the  bend  is  slight,  A  can  be  most  easily  made  parallel  to  B  by 
filing,  but  when  badly  bent  it  should  be  carefully  straightened. 

The  jaws  of  the  wrench  and  the  nut  or  square  upon  which  it 


FIGS.    126  AND  127. 


is  being  used  will  be  least  injured  when  the  jaws  are  closed 
firmly  on  the  work.  This  necessitates  slackening  them  slightly 
and  closing  again  every  time  the  wrench  is  changed.  By  giving 
the  hand  a  slight  rolling  motion  around  the  handle,  with  the  fore- 
finger against  the  knurled  head  of  the  wrrench  screw,  a  sufficient 
amount  of  motion  can  be  given  to  the  sliding  jaw  to  close  on 
and  release  from  the  work  without  loss  of  time. 

The  sliding  jaw,  due  to  its  long  bearing  on  the  shank,  is  much 
stronger  than  the  fixed  jaw,  consequently  the  wrench  should  be 
operated  in  the  direction  of  the  arrow,  Fig.  126.  An  examina- 
tion of  Fig.  127  shows  that  when  turned  as  above  indicated  the 
maximum  pressure  comes  at  B  and  C,  which  places  the  shorter 


102 


MODERN    MACHINE    SHOP    TOOLS. 


leverage  on  the  weaker  jaw.  If  turned  in  the  opposite  direc- 
tion the  pressure  comes  at  D  and  E,  which  increases  the  bending 
tendency  at  F,  and  also  the  pressure  on  the  screw. 

The  great  variety  of  combination  wrenches  on  the  market  pos- 
sess little  merit.  When  we  use  a  wrench  we  do  not  want  to  have 
a  hammer,  a  screw  driver,  a  nail  puller,  and  a  dozen  other  ''useful 
tools"  in  our  way  at  one  time. 

When  finished  standard  nuts  are  to  be  turned  the  solid  wrench 
is  preferable  to  the  adjustable,  as  it  can  be  made  to  fit  closely 
to  the  nut  with  less  danger  of  injuring  it.  In  Fig.  128  is  shown 
a  finished  case-hardened,  solid  wrench.  The  angle  of  the  open 
end  is  fifteen  degrees  with  the  length  of  the  handle,  which  enables 
a  hexagon  nut  to  be  turned  when  the  wrench  can  be  carried 


FIGS.    128  TO  132. 

through  thirty  degrees  only.  These  wrenches  may  be  had  double 
ended.  The  box  wrench  has  a  closed  opening,  as  shown  in  Fig. 
129.  This  particular  form  is  commonly  called  a  tool  post  wrench. 

The  socket  wrench,  shown  in  Fig.  130,  is  made  for  square  and 
hexagon  nuts  and  cap  screws,  which  are  to  be  operated  upon  in 
deep  or  inaccessible  places.  Wlien  a  great  many  small  nuts  are 
to  be  quickly  set,  the  socket  wrench,  in  Fig.  131,  operated  in  a 
bit  brace,,  does  the  work  rapidly. 

It  frequently  happens  that  a  nut  must  be  turned  which  is  in 
so  inaccessible  a  place  that  the  handle  of  the  wrench  can  be  car- 
ried through  only  a  few  degrees.  In  such  cases,  the  ratchet 
wrench,  shown  in  Fig.  132,  serves  its  purpose  well,  the  effect  on 
the  nut  being  much  more  satisfactory  than  when  the  set  chisel 
and  hammer  are  used.  In  the  use  of  all  solid  wrenches  they 
must  fit  the  nut  closely,  as  otherwise  both  nut  and  wrench  will 
be  injured,  the  nut  rounding  and  the  wrench  spreading. 


CHAPTER   VIII. 

DRILLS 

The  twist  drill  which  has  come  into  such  universal  use,  has 
superseded  the  old,  flat,  forged  drill  which,  for  so  many  years, 
held  without  rival  the  first  position  as  a  tool  for  producing  cir- 
cular holes  in  metal.  For  the  needs  of  its  day,  it  served  its  purpose 
well.  The  advancements  along  mechanical  lines  demanded  a 
better  tool  for  this  work,  however,  and  the  twist  drill  resulted, 
brought  out  in  practically  the  same  form  as  now  used,  the  prin- 
cipal recent  improvements  being  mostly  in  slight  changes  in 
form,  and  its  more  accurate  production  due  to  improved  methods 
of  manufacture. 

The  flat  drill,  as  used  for  metal  work,  is  generally  of  the  form 
shown  in  Fig.  133.  It  is  made  from  round  stock,  is  forged  thin  at 


FIG.  133. 

the  lips,  and  ground  as  shown  in  the  figure,  with  three  cutting 
edges — A,  B  and  C.  This  is  a  very  accommodating  sort  of  a1  tool, 
being  capable  of  producing  a  number  of  holes  of  different  diam- 
eters, yet,  approximately  equal  to  the  width  of  the  drill.  The  dis- 
advantage of  this  adjustability,  however,  lies  in  the  fact 'that  the 
size  of  hole  wanted  cannot  ordinarily  be  produced. 

The  flat  drill  has  no  lands,  as  that  part  of  the  twist  drill  be- 
tween flutes  is  called,  to  steady  and  guide  it  in  the  work.  Conse- 
quently, the  hole  drilled  will  usually  not  be  round,  and  should  the 
point  of  the  drill  strike  the  side  of  a  small  blow  hole  or  soft  spot 
in  the  metal  being  drilled,  as  frequently  happens  in  working  cast 


104 


MODERN    MACHINE    SHOP    TOOLS. 


metal,  the  point  will  drift  toward  this  spot,  thus  making  a  hole 
that  is  neither  round  nor  straight.  This  is  shown  at  A  in  Fig.  134. 

In  order  to  drill  holes  approximately  to  size  with  the  flat  drill, 
it  is  necessary  that  the  cutting  lips  be  most  carefully  ground.  The 
angle  of  the  lips  with  the  axis  of  the  drill  must  be  equal,  other- 
wise one  cutting  edge  will  perform  all  the  work,  and  will  dull 
quickly,  due  to  this  double  duty.  The  pressure  on  the  cutting  lip 
will  crowd  the  point,  causing  it  to  revolve  in  a  small  circle  about 
the  center  of  revolution.  This  will  cause  the  other  flute  to  cut 
slightly  at  its  outer  end,  thus  producing  a  hole  of  larger  diameter 
than  the  width  of  flat.  This  is  shown  at  B,  in  Fig.  134. 

The  cutting  lips  should  be  of  equal  length,  with  their  intersec- 
tion in  the  axis  of  rotation  of  the  drill.  If  one  lip  is  longer  than 
the  other,  the  diameter  of  the  hole  drilled  will  depend  on  the 


length  of  this  long  lip,  as  it  will  rotate  about  C,  its  central  axis, 
as  shown  at  A,  in  Fig.  135. 

In  case  the  intersection  of  the  lips  does  not  fall  on  the  axis 
of  the  drill,  the  one  lip  is  thereby  made  longer  than  the  other, 
and  the  hole  drilled  will  again  be  large,  as  the  tool  will  spring  an 
amount  sufficient  to  allow  it  to  revolve  about  C  instead  of  its  true 
axis,  and  the  length  of  the  long  flute  again  determines  the  diam- 
eter of  the  hole  drilled,  as  shown  at  B,  in  Fig.  135. 

The  first  cost  of  the  flat  drill  is  small,  and  the  results  obtained 
by  its  use  usually  poor.  Its  only  advantage  lies  in  the  fact  that 
it  can  readily  be  forged  and  tempered  to  do  work  on  extremely 
hard  metals.  The  flat  drill,  ground  thin  and  tempered  hard,  is  a 
valuable  tool  for  drilling  hard  steel  or  chilled  iron,  as  it  will  in 
that  form  take  hold  of  metal  that  the  twist  drill  will  not  touch. 
It  also  makes  a  convenient  extension  drill,  as  it  can  be  readily 
formed  on  the  end  of  a  long  bar  of  steel. 


DRILLS.  IO5 

The  flat  drill  is  not  adapted  to  the  drilling  of  deep  holes,  as  it 
does  not  free  itself  of  chips.  It  is  largely  used  for  roughing  out 
cored  holes,  preparatory  to  boring,  which  work  is  very  destruc- 
tive, due  to  scale  and  sand,  to  the  land  clearances  of  twist  drills. 
When  so  used  in  a  lathe,  the  drill  is  held  against  the  dead  center 
and  fed  forward  by  the  tail  screw,  the  work  revolving. 

About  1860,  twist  drills,  having  milled  flutes,  were  first  placed 


FIG.  135. 

on  the  market.  Previous  to  this  date,  however,  drills  with  flutes 
produced  by  filing  and  the  twisting  of  the  flat  stock  had  been 
used  to  a  limited  extent. 

In  Fig.  136  is  shown  a  taper  shank  twist  drill.  A  A  are  the 
flutes,  B  B  the  lands,  C — the  metal  between  the  flutes — the  web, 
D  D  the  lips,  E  the  shank  and  F  the  tang.  The  center  or  grinding 
line  is  the  fine  line  running  along  the  bottom  of  each  flute,  and 


FIG.  136. 

serves  as  a  guide  to  the  lips  in  grinding  so  their  intersection  will 
fall  in  the  center  of  the  drill. 

The  three  clearances  in  the  twist  drill  are :  first,  the  "body 
clearance"  of  one-half  to  one-thousandth  of  an  inch  per  inch  of 
length  of  the  fluted  portion ;  second,  the  "land  clearance"  of  about 
one-half  of  one  circular  degree  as  shown  at  A  A  in  the  end  view, 
Fig.  137,  and  last,  the  "lip  clearance"  made  by  grinding  back  the 
ends  G  G  of  the  lands,  Fig.  137,  to  properly  clear  the  cutting 
edges  H  H. 

There  are  three  cutting  edges,  H,  H  and  C ;  of  these  C  is  the 


io6 


MODERN    MACHINE    SHOP    TOOLS. 


least  effective,  as  it  is  not  a  free  cutting  edge  and  grinds  rather 
than  cuts  the  metal.  By  reducing  the  thickness  of  the  web  at 
the  point  as  shown  in  Fig.  138,  thus  making  the  cutting  edge  C 
short,  the  efficiency  of  the  drill  is  materially  improved.  This  is 
of  greatest  value  with  drills  of  large  diameter  where  the  webs  are 
made  thick  to  give  the  necessary  strength.  The  points  may  be 
thus  thinned  by  grinding  on  a  small  emery  wheel. 

The  flutes  of  twist  drills  as  usually  manufactured  are  cut  by 
milling  from  stock  of  round  cross  section.  Numerous  attempts 
have  been  made  to  produce  a  satisfactory  hot  rolled  drill,  in  which 
the  flutes  are  formed  by  passing  the  stock  which  is  rectangular  in 
cross  section  and  heated  to  a  forging  point,  through  spiral  rolls. 
A  hot  forged  drill  has  recently  been  placed  on  the  market.  In 


FIG.  138. 


FIG.   139. 


this  tool  the  flutes  and  twist  are  produced  by  forging,  and  great 
strength  and  durability  of  cutting  edges  are  the  claims  for  it  by 
the  manufacturers. 

In  order  to  give  the  drill  greater  strength  toward  the  shank, 
the  web  is  increased  in  thickness  from  the  point  to  the  end  of  the 
flute.  This  thickening  of  the  web  is  accomplished  by  gradually 
withdrawing  the  milling  cutter  from  the  blank  as  the  cut  ad- 
vances. This  makes  the  flute  shallower  at  its  upper  end,  with  a 
gradually  decreasing  area  of  cross  section  from  the  point  to  the 
shank.  This  contraction  of  the  flute  area  prevents  the  free  de- 
livery of  the  chips  and  consequent  clogging  of  the  drill.  It  is 
therefore  necessary  to  make  the  flute  area  equal  throughout  its 
entire  length.  This  is  usually  accomplished  by  making  the  pitch 
of  the  flute  spiral  uniformly  greater  from  point  to  shank,  and  is 


DRILLS.  lO/ 

known  as  an  "increase  .twist"  drill.  It  is  also  produced  by 
giving  the  flute  a  spiral  of  "constant  angle,"  and  increasing  the 
width  of  flute  toward  the  shank.  This  latter  result  is  obtained 
by  slightly  changing  the  angle  of  the  arbor  carrying  the  flute 
cutting  mill  with  the  axis  of  the  drill  blank  as  the  cut  advances, 
and  the  mill  is  receded  from  the  blank,  in  giving  a  web  of  in- 
creased thickness.  This  latter  method  makes  the  lands  narrower 
at  the  shank  end  of  the  flute  and  thereby  reduces  somewhat  the 
strength  of  the  drill.  On  the  other  hand,  it  possesses  the  ad- 
vantage of  giving  a  constant  angle  of  rake  to  the  cutting  lips 
as  the  length  of  the  drill  decreases.  This  is  shown  in  Fig.  139, 
where  the  angle  of  rake  is  27^  degrees  for  either  form  of  drill 
when  the  tool  is  new.  When  worn  nearly  to  the  shank,  this 
angle  in  the  "increased  twist"  drill  is  materially  decreased,  while 
for  the  "constant  angle"  drill,  it  remains  the  same. 

For  the  small  drills,  the  blanks  are  usually  made  from  steel 


FIG.  140. 

wire.  They  are  first  cut  in  lengths  and  then  given  a  body  clearance 
by  filing.  The  flutes  are  each  cut  separately.  With  the  drills  of 
larger  diameter,  the  blanks  are  turned  in  a  lathe  and  finished  to 
exact  diameter  by  filing.  In  cutting,  they  are  held  upright  in  a 
vertical  machine,  both  flutes  being  cut  at  the  same  time.  The 
clearance  of  the  lands  is  made  by  either  milling  or  grinding, 
and  with  the  large  drills  both  lands  are  relieved  at  the  same  time. 

Drills  are  given  a  cutting  temper  the  entire  length  of  the  flutes, 
and  are  carefully  straightened  after  this  process. 

Twist  drills  are  sometimes  made  slightly  over  size,  and  after 
tempering  are  ground  perfectly  straight.  This  adds  little  to  the 
value  over  the  properly  straightened  drill  and  increases  consider- 
ably the  cost. 

Twist  drills  having  more  than  two  flutes  ar-j  frequently  used 
for  enlarging  drilled  or  cored  holes.  They  are  very  efficient  for 
this  purpose,  but  as  the  lips  do  not  intersect  at  the  point,  they 
cannot  drill  a  hole  from  the  solid  stock.  A  three  flute  twist  drill 
is  shown  in  Fig.  140.  They  are  regularly  made  in  sizes  from  V$ 
inch  to  3  inches,  varying  by  thirty-seconds.  The  straight  flute 


io8 


MODERN    MACHINE    SHOP    TOOLS. 


drill  is  one  having  the  flutes  cut  parallel  to  the  axis  of  the  drill,  and 
is  in  other  respects  similar  to  the  twist  drill.  A  straight  flute 
drill  is  shown  in  Fig.  141.  In  Fig.  142  is  shown  a  hollow  drill 
which  may  be  used  to  advantage  in  the  drilling  of  deep  or  long 
holes,  the  chips  passing  out  through  the  hollow  shank. 

Great  care  must  be  exercised  in  grinding  the  twist  drill,  as  the 


FIG.  141. 

same  troubles  on  a  smaller  scale  as  those  shown  in  Figs.  134  and 
135  for  the  flat  drill  will  result  from  the  improper  grinding  of 
the  twist  drill.  The  angle  of  Up  clearance  should  be  greater 
at  the  center  than  at  the  outer  ends  of  the  lips  and  must  not  be 
excessive,  as  in  that  case  the  drill  bites  too  rank.  If  this  angle  is 
too  small,  however,  the  cut  is  not  free  and  excessive  heating  re- 


FIG.  142. 

suits.  The  angle  of  the  lip  to  the  axis  of  the  drill  should  be  59 
degrees.  This  gives  a  straight  cutting  lip  as  shown  in  end  view, 
Fig-  137.  There  are  a  number  of  drill  grinders  made  that  will 
grind  drills  satisfactorily.  The  experienced  mechanic  usually 
prefers  to  grind  his  drills  by  hand,  depending  upon  his  eye  and 


judgment  for  the  proper  angles  and  clearance.     It  is  in  this  way 
that  all  new  drills  are  ground  before  leaving  the  factory. 

The  standard  shanks  for  drills  are  straight  and  taper.     The 
taper  shank  is  shown  in  Fig.   136.     It  is  made  in  six  sizes,  and 


DRILLS. 


109 


known  as  the  Morse  taper,  which  is  approximately  y%  inch  per 
foot.  The  exact  taper  for  the  several  sizes  is  given  in  the  follow- 
ing table ;  also  the  limiting  sizes  of  drills  on  which  each  taper  is 
generally  used : 

TABLE  OF  MORSE  TAPERS. 


No.  of  Taper. 

Taper  per  foot. 

Smallest  Drill  using 
each  Taper. 

Largest  Drill  using 
each  Taper. 

i 

2 

3 

.605 
.600 
.605 

I/ 

1 

4 

.615 

iff 

2 

5 

.625 

2<k 

3 

6 

•  634 

Special. 

Special. 

In  Fig.  143  is  shown  the  shank  of  what  is  known  as  the 
grooved  shank  drill  to  be  held  in  a  special  chuck.  These  grooves 
may  also  be  applied  to  taper  shanks.  Drills  are  also  made  with 
square  shanks  to  be  held  in  ratchets  and  bit  braces,  also  with  shanks 
of  various  special  forms. 

Taper  shank  drills  are  made  and  carried  in  stock  by  1-64  inch 
sizes  from  ^  of  an  inch  to  2,y2  inches,  and  by  1-16  inch  sizes  from 
2^/2  inches  to  3  inches.  All  sizes  over  3  inches  are  special  and 
made  only  to  order.  Straight  shank  drills  are  made  by  1-64  inch 
sizes  from  1-16  of  an  inch  to  2.y2  inches.  A  regular  straight  shank 
drill  is  the  same  length  over  all  as  a  taper  shank.  What  are 
known,  however,  as  jobbers'  sets,  running  from  1-16  of  an  inch 
to  y*  inch  by  64ths,  are  considerably  shorter  than  the  regular 
lengths.  The  wire  gauge  sizes  run  from  No.  80 — the  smallest 
twist  drill  regularly  made — to  No.  i.  The  Xo.  i  wire  gauge  drill 
is  .228  or  about  15-64  of  an  inch  in  diameter,  while  the  No.  80 
is  but  .0135,  or  a  little  more  than  i-ioo  of  an  inch  in  diameten 
This  latter  drill  is  an  exceedingly  delicate  little  tool,  having  flutes 
quite  perfectly  formed. 

Drills  are  made  in  what  are  known  as  letter  sizes,  from  A  to  Z, 
A  being  the  smallest,  .234  of  an  inch,  and  Z  the  largest,  .413  of  an 
inch.  These  drills  are  made  with  straight  shanks.  Millimeter 
sizes  from  6  to  50  m.m.  are  made  by  most  American  makers. 
From  6  to  25  m.m.  sizes  increase  by  j/2  m.m.  advances.  The  milli- 
meter drills  are  made  in  both  straight  and  taper  shanks. 

It  has  not  been  found  practical  to  give  drills  smaller  than  No. 
74  wire  gauge,  .0225  of  an  inch,  land  clearance,  and  many  drills 
considerably  larger  than  this  are  not  so  cleared. 


no 


MODERN    MACHINE    SHOP    TOOLS. 


Practice  is  somewhat  at  variance  as  to  the  best  speeds  at  which 
to  run  drills.  The  later  tendencies  are  to  reduce  the  feeds  and 
increase  the  number  of  revolutions,  that  is  for  the  smaller  sizes. 
For  the  larger  sizes,  the  number  of  revolutions  varies  little  from 


TABLE    OF   DRILL  SPEEDS. 


Diameter  of  Drills. 

Speed  for  Wrought 
Iron  and  Steel. 

Speed  for  Cast  Iron. 

Speed  for  Brass. 

11g-  inch. 

1712 

2383 

3544 

X 

855 

1191 

1772 

H 

397 

565 

855 

% 

265 

375 

570 

% 

183 

267 

412 

% 

147 

214 

330 

% 

112 

168 

265 

Y* 

96 

144 

227 

i 

76 

H5 

191 

i# 

68 

102 

170 

i* 

58 

89 

150 

i# 

53 

81 

136 

i^ 

46 

74 

122 

i% 

40 

66 

H3 

i3* 

37 

61 

105 

i# 

33 

55 

98 

2 

3i 

5i 

92 

the  old  practice.  The  above  table  gives  the  speed  of  drills  in 
revolutions  per  minute  as  recommended  by  a  leading  manufac- 
turer of  drills. 

A  rule  that  is  easily  remembered  and  gives  approximately  the 
correct  speed  is,  dividing  80,  no  and  180  by  the  diameter  of 
drill,  will  give  the  number  of  revolutions  per  minute  for  work  on 
steel,  cast  iron  and  brass  respectively.  The  results  will  be  rather 
low  for  the  smaller  sizes  and  high  for  the  larger  sizes. 

The  feeds  for  drills  should  vary  with  the  diameter  of  the  drill 
and  the  hardness  of  the  metal  being  drilled,  and  will  usually  be 
i -200  to  1-50  of  an  inch  per  revolution  of  the  drill. 

In  drilling  wrought  iron  or  steel,  the  drill  should  be  flooded 
with  oil,  or  some  suitable  drilling  compound,  which  lubricates 
the  cutting  edge  and  carries  away  the  heat  of  friction.  Cast  iron 
and  brass  are  drilled  dry. 

A  drill  with  cutting  lips  having  no  angle  of  rake  will  work  best 
in  brass.  A  straight  flute  drill  or  twist  drill  with  lips  ground  as 
shown  in  Fig.  144,  is  well  suited  to  this  work. 

In  drilling  deep  holes  in  steel,  especially  when  the  drill  is  held 


DRILLS. 


Ill 


in  a  horizontal  position,  it  is  difficult  to  properly  lubricate  the 
cutting  edges  of  the  drill.     To  overcome  this,  oil  tube  drills — 
one  of  which  is  shown  in  Fig.  145 — are  being  very  successfully 
used.    In  this  drill  oil  is  forced  to  the  cutting  lips,  thus  thoroughly 
lubricating  them,  at  the  same  time  helping  to  force  out  the  chips 
and   keep   down   the   temperature.        The   usual 
method    of   making   this    drill   is   to   mill    small 
grooves  in  the  lands  parallel  to  the  flutes  and  se- 
cure,  by   solder,    in    these   grooves    small   tubes 
which,  at  the  shank   end,   are  usually   made  to 
open  into  a  hollow  in  the  shank  from  which  suit- 
able connection  is  made  with  the  oil  supply.     One 
manufacturer  uses  the  following  unique  method 
for  producing  these  oil  passages.       Two  small 
holes  are  drilled  parallel  to  the  axis  in  the  stock 
from  which  the  tool  is  to  be  made.     The  length 
of  these  holes  is  somewhat  more  than  the  length 
of  the  grooved  portion  of  the  finished  tool,  so  as 
to  connect  with  the  hollow  shank.     After  these  holes  are  finished 
the  stock  is  heated  to  a  low  forging  temperature  and  then  twisted 


FIG.  144. 


FIG.   145. 


an  amount  such  as  to  make  the  holes  come  parallel  with  the  flutes 
when  cut.     A  cut  of  this  drill  is  shown:  in  Fig.  146. 

Oil  tube  drills  are  necessarily  expensive  to  manufacture :   their 


FIG.  146. 


use  will,  however,  frequently  more  than  double  the  output  of  the 
machine  driving  them. 

The  drilling  of  holes  that  are  to  be  tapped  requires  a  drill  equal 
in  diameter  to  the  root  diameter  of  the  tap,  and  is  called  a  tap 


112 


MODERN    MACHINE    SHOP   TOOLS. 


drill.  The  machinist  soon  fixes  in  his  mind  the  proper  tap  drills 
for  the  taps  he  most  uses.  When  there  is  any  uncertainty  as  to 
the  proper  diameter,  consult  a  table  of  tap  drill  sizes  or  caliper 
the  end  of  the  taper  tap,  and  select  a  drill  that  will  just  allow  the 
point  of  tap  to  enter ;  this  will  give  a  full  thread.  The  following 
table  gives  the  sizes  of  tap  drills  from  l/\.  of  an  inch  to  i^  inches 
for  the  V  and  United  States  Standard  threads.  The  United  States 
Standard  number  of  threads  per  inch  are  those  taken. 

TAP    DRILL    TABLE. 


Diameter  of  Tap. 

No.  of  Threads. 

Drill  for  U.  S.  S. 
Thiead 

Drill  for  V  Thread. 

y 

20 

M 

& 

78 

18 
16 

V 

i 

TV 

14 

fi 

¥ 

13 

ff 

12 

7_ 

iV 

/^ 

II 

/^ 

M 

^ 

10 

^ 

it 

% 

9 

|4 

tHr 

i 

8 

|| 

T! 

\y% 

1 

if 

ft 

ii^  * 

-1 

IyV 

i« 

ll£ 

6 

IJL 

i^ 

'K 

6 

'ff 

*** 

The  location  of  a  hole  to  be  drilled  is  usually  indicated  by  a 
center  punch  mark ;  if  the  hole  must  be  drilled  exact  to  this  center 
a  circle  of  diameter  equal  to  the  diameter  of  the  hole  to  be  drilled 
should  be  described  about  the  punch  mark  as  a  center,  as  shown 
at  A  in  Fig.  147.  A  few  light  prick  punch  marks  should  be  made, 


B 


FIG.   147- 


A  A  A  A,  on  this  circle.  If  the  drill  runs  to  one  side  as  shown 
at  B  in  Fig.  147,  it  can  be  drawn  back  by  cutting  away  the  wide 
edge  with  a  cape  chisel  as  shown  at  B ;  this  chisel  cut  should  run 


DRILLS.  113 

to  the  center.  The  drill  must  be  brought  concentric  with  the 
circle  A  A  A  A  in  this  manner  before  it  begins  to  cut  the  full 
diameter,  as  it  cannot  then  be  readily  shifted.  When  the  surface 
upon  which  tne  holes  are  laid  out  is  a  machined  one,  it  is  often 
better  to  scribe  a  circle  about  the  center  mark  slightly  larger  in 
diameter  than  the  required  hole  and  drill  to  the  center  of  this 
circle.  This  leaves  the  laying  out  circle  on  the  work  and  readily 
shows  any  inaccuracy  in  the  drilling. 

The  laying  out  and  drilling  of  holes  in  this  manner  when  ac- 
curate location  is  necessary,  requires  care  and  skill  -and  is  usually 
an  expensive  operation.  When  many  similar  pieces  are  to  be  so 
drilled,  it  is  usual  to  provide  a  suitable  jig  or  drilling  template, 
which  insures  accuracy  and  requires  very  much  less  time.  The 
subject  of  jig  drilling  is  taken  up  in  Chapter  XXVII.  On  a  large 
amount  of  drilling  work  the  hole  in  one  part  serves  as  a  guide 
for  drilling  other  holes  in  other  parts  of  the  work,  and  in  many 
cases  it  is  possible  to  use  one  piece  of  work,  which  has  been  care- 
fully laid  out  and  drilled,  as  a  template  for  drilling  other  similar 
pieces. 

WThen  the  point  of  the  drill  breaks  through  the  work  and  the 
pressure  is  thereby  greatly  reduced,  care  must  be  exercised  in 
the  handling  of  the  feeds  to  prevent  the  drill  from  worming  or 
drawing  through  without  cutting  the  full  circle.  In  case  this 
occurs,  one  of  three  things  will  certainly  result :  break  the  work, 
the  drill  or  stall  the  machine.  A  straight  flute  drill  or  a  twist 
drill  with  lips  ground  as  shown  in  Fig.  144  will  not  worm  through 
and  are  good  tools  to  use  for  drilling  thin  or  sheet  metals. 

Keep  the  drill  sharp  by  proper  grinding. 


CHAPTER  IX. 

REAMERS. 

In  order  to  produce  holes  as  round,  straight,  smooth  and  uni- 
form in  diameter  as  is  required  in  the  construction  of  accurate 
machinery,  a  reamer  must  be  used.  As  has  been  shown  in  a  pre- 
ceding article,  the  drill  cannot  be  relied  upon  to  produce  holes 
possessing  the  above  qualities. 

A  reamer  is  a  sizing  tool  having  two  or  more  teeth  either  par- 
allel or  at  an  angle  with  each  other,  the  latter  forming  what  is 
known  as  a  taper  reamer.  These  teeth  may  be  either  straight  or 
spiral;  a  spiral  tooth  producing  a  shearing  cut,  while  a  straight 
tooth  gives  a  square  cut. 

As  to  their  construction,  reamers  for  producing  parallel  holes 
may  be  divided  under  two  general  heads — solid  and  adjustable. 
All  taper  reamers  come  under  the  solid  class.  A  solid  reamer  is 
one  having  a  shank  and  teeth  made  from  a  single  piece  of  tool 
steel.  The  expansion  reamer  is  a  built-up  tool,  the  usual  form 
consisting  of  a  shank  and  head,  the  head  having  suitable  recesses 
in  which  are  secured  the  cutting  teeth.  As  adjustment  to  com- 
pensate for  wear  only  is  attempted,  the  amount  of  expansion  is 
small. 

The  number  of  teeth,  their  form  and  spacing  are  the  important 
•considerations  in  the  construction  of  this  tool.  Reamers  having 
fewer  than  five  teeth  are  not  to  be  used  where  accurate  cylindrical 
truth  is  desired.  A  reamer  having  three  teeth  cannot  be  de- 
pended upon  to  produce  round  holes,  inasmuch  as  any  irregu- 
larity in  the  hole  being  reamed  affects  the  cutting  of  the  tool. 
This  is  shown  in  Fig.  148,  where  a  depression  A  exists  in  the 
drilled  hole.  When  the  tooth  B  comes  to  this  point  it  drops  in, 
thus  decreasing  the  cutting  of  C  and  D,  and  produces  a  hole  not 
round.  The  same  effect  to  a  lesser  degree  is  produced  in  a  reamer 
having  four  teeth,  Fig.  149.  When  the  cut  is  relieved  at  A,  the 
pressure  of  the  cut  at  C  will  crowd  the  tool  toward  E.  Since  the 
pressure  of  cut  at  B  and  D  balance  each  other,  any  decrease  of 
cut  at  C  causes  an  increase  at  D,  and  B  and  C  will  overbalance  D, 
the  body  of  the  reamer  moving  an  appreciable  distance  toward 


REAMERS.  115 

"E.  With  five  or  more  teeth  this  effect  practically  disappears.  The 
more  cutting  edges,  the  more  smoothly  will  the  reamer  work. 
The  construction  of  adjustable  reamers  does  not  admit  of  as  many 
teeth  as  can  be  formed  on  a  solid  reamer,  yet  the  advantage  of 
adjustability  to  a  certain  extent  offsets  this. 

Reamers  having  an  even  number  of  teeth  equally  spaced  do  not 
produce  as  good  results  as  those  having  an  odd  number  of  teeth. 
In  the  former,  the  teeth  fall  opposite  each  other,  causing  greater 
tendencies  to  vibration,  and  in  the  case  of  reaming  irregular  holes, 
the  greatest  cut  will  be  carried  on  two  opposite  teeth ;  but  with  an 
odd  number  of  teeth,  the  greatest  cut  must  be  carried  on  at  least 
three  teeth. 

Reamers  having  an  even  number  of  teeth  but  irregularly  spaced 
are  verv  extensively  made.  A  cross-section  of  such  a  tool  is 


FIG.  148. 


FIG.  149. 


FIG.   150. 


FIG.  151 


FIG    I?2. 


shown  in  Fig.  150.  The  effect  is  practically  the  same  as  having  an 
odd  number  of  teeth. 

The  form  of  tooth  usually  employed  is  shown  in  Fig.  151.  The 
front  face  is  on  a  radial  line,  the  flute  being  well  filleted  at  the 
root.  If  an  angle  of  rake  is  given  the  tooth,  as  shown  in  Fig.  152, 
and  specially  so  if  the  fillet  at  root  is  cut  away,  the  tooth  will 
spring  out  under  the  cut,  producing  an  oversize  hole. 

The  grinding  of  the  clearance  on  top  of  the  tooth  is  an  impor- 
tant point  in  the  construction  of  a  reamer.  The  clearance  should 
be  sufficient  to  properly  relieve  the  cutting  edge.  If  too  great 
clearance  is  given,  the  tooth  will  be  weak  and  chatter  in  the  work. 
As  frequently  produced,  the  cleared  surface  is  slightly  concave, 
the  amount  depending  on  the  diameter  of  the  emery  wheel  used 
in  grinding  it.  As  a  plain  surface  is  desirable,  a  wheel  of  large 
diameter  which  gives  approximately  such  a  surface,  should  be 
employed,  or  better  still  the  face  of  a  cup  emery  wheel  which  gives 
a  straight  clearance 


n6 


MODERN    MACHINE   SHOP    TOOLS. 


The  angle  of  clearance  will  depend  on  the  distance  the  axis  of 
the  emery  wheel  is  set  back  of  the  axis  of  the  reamer,  as  shown 
in  Fig.  153.  In  no  case  must  the  wheel  come  in  contact  with  the 
front  face  of  the  tooth  being  ground  or  the  one  next  behind,  and 
the  guiding  finger  which  steadies  the  reamer  must  always  bear 
against  the  front  face  of  the  tooth  being  ground.  When  the 
diameter  of  the  reamer  is  large  and  the  pitch  of  the  teeth  so  small 
that  the  necessary  clearance  cannot  be  given  except  by  using  too 
small  an  emery  wheel,  the  wheel  can  be  mounted  on  an  axis  at  a 
considerable  angle  with  the  axis  of  the  reamer,  as  shown  in  Fig. 
154.  This  produces  a  plane  surface;  but  due  to  the  wear  of  the 
emery  wheel  is  not  as  satisfactory  as  the  use  of  the  cup  wheel. 
The  wheel  must  be  so  placed  as  to  cut  its  entire  width,  other- 


FIG.  153. 


FIG.   154. 


wise  it  will  be  grooved  and  the  cutting  edges  of  the  tooth  round- 
ed off. 

A  hand  reamer  is  a  tool  for  hand  use ;  while  a  chucking  reamer 
is  operated  in  a  machine.     Fig.   155  illustrates  a  standard  solid 


FIG.   155. 


hand  reamer.    In  its  manufacture,  the  stock  is  first  cut  to  length 
and  then  turned  to  a  diameter  about  1-64  inch  over  finish  size. 


REAMERS.  117 

The  flutes  and  square  on  the  end  of  shank  are  next  cut  by  milling 
processes.  Tempering  is  the  next  operation,  from  which  it  usually 
comes  warped  to  a  greater  or  less  extent.  After  straightening, 
the  centers  are  lapped  out  and  the  reamer  ground  in  a  grinding 
machine  to  diameter  and  cylindrically  true.  All  standard  reamers 
are  made  .0005  of  an  inch  over  size.  This  is  because  a  new  reamer, 
before  being  used,  should  have  its  cutting  edges  stoned  slightly, 
which  will  just  about  bring  it  down  to  exact  diameter.  If.  this  is 
not  done,  the  edges  will  give  down  a  little  on  the  first  few  holes 
reamed ;  so  that  if  the  reamer  was  made  to  exact  diameter  it 
would  fall  below  size  too  quickly.  The  shank  is  usually  ground 
about  .001  of  an  inch  smaller  than  the  fluted  portion,  and  in  its 
use  serves  as  a  gauge  to  indicate  when  the  reamer  has  fallen, 
through  wear,  below  .00 1  of  an  inch  under  size.  The  shank  should 
not  be  marred  in  any  way,  as  in  that  case  the  purpose  for  which 
it  was  so  carefully  brought  to  size  is  lost,  and  in  cases  where  the 
reamer  is  passed  through  the  work,  damage  to  the  hole  is  apt  to 
result.  The  last  operation  previous  to  grinding  the  clearance  and 
final  inspection  in  the  manufacture  of  a  reamer  is  the  buffing  out  of 
the  flutes.  This  is  done  by  passing  them  under  a  small  vulcan- 
ized emery  wheel,,  which  has  first  been  trued  to  the  exact  outline 
of  the  flute. 

The  hand  reamers  are  regularly  made  in  two  lengths ;  what  is 
known  as  the  short  reamer  being  considerably  shorter  both  in 
the  flute  and  shank  than  the  regular  or  jobber's  reamer.  The 
diameter  of  the  point  is  about  1-64  of  an  inch  under  size,  the  tool 
tapering  to  exact  diameter  at  about  one-fourth  the  length  of  the 
tooth  from  the  point.  The  balance  of  the  teeth  are  ground  nearly 
parallel,  the  diameter  at  the  shank  end  being  from  .0005  to  .00075 
of  an  inch  small.  This  slight  taper  counteracts  the  tendency  that 
all  reamers  have  to  ream  a  hole  slightly  over  size  at  the  top, 
which  is  due  to  the  tool  remaining  longer  in  contact  with  the 
wall  of  the  hole  at  the  top  than  at  the  bottom.  The  limit  of 
error  allowed  in  their  manufacture  does  not  exceed  .00025  of  an 
inch. 

\Yhen,  for  the  parallel  shank  of  the  hand  reamer,  a  taper  shank 
is  substituted,  the  reamer  becomes  adapted  to  use  in  a  drill  press 
or  other  machine.  The  form  and  length  of  flute  is  the  same  as  for 
the  regular  hand  reamer,  except  at  the  point,  where  the  teeth 
instead  of  tapering  for  one-fourth  of  the  length  of  the  flute,  run 
parallel  to  the  point.  This  form  is  used  because  the  reamer  cuts 


MODERN    MACHINE    SHOP    TOOLS. 


easier  and  faster,  and  as  it  is  steadied  by  the  spindle,  no  difficulty 
is  experienced  in  starting  it  true. 

In  Fig.  156  is  shown  a  spiral  fluted  reamer.     They  are  always 


FIG.  156. 

cut  with  a  left-hand  spiral.  They  give  a  smooth  shearing  cut  and 
are  specially  valuable  for  machine  reaming  on  centers  as  they  do 
not  tend  to  draw  into  the  work  and  off  from  the  center.  They  are 
also  made  in  shell  and  taper. 

Fig.  157  illustrates  a  fluted  chucking  reamer  with  taper  shank. 


FIG.  157. 

The  total  length  of  this  tool  is  approximately  the  same  as  the 
length  of  a  hand  reamer.  The  teeth  are  short  and  slightly  tapered 
at  the  point,  which  facilitates  starting  when  used  against  the 
dead  center  of  a  lathe.  It  is  also  made  with  straight  shank. 

The  rose  chucking  reamer,  Fig.  158,  is  of  the  same  length  and 


FIG.  158. 

provided  with  the  same  forms  of  shank  as  a  fluted  chucking 
reamer.  The  head  is  ground  cylindrical  with  cutting  teeth  on 
the  end.  The  circular  flutes  do  not  form  cutting  edges,  their  office 
being  to  carry  the  lubricants  to  the  point  of  the  tool,  and,  espe- 
cially when  used  in  a  horizontal  position,  to  carry  away  the  chips. 
It  is  therefore  important  that  a  flute  be  provided  for  each  cutting 
lip.  The  head  is  given  only  a  slight  clearance  in  its  length.  The 
result  is  that  holes  produced  with  the  rose  reamer  are  usually 
round  and  straight,  but  not  so  smooth  as  those  formed  by  longer 


REAMERS. 


119 


cutting  edges.  The  lack  of  clearance  in  this  tool  makes  it  unsuit- 
able for  reaming  deep  holes,  as  a  small  amount  of  heat  causes  it 
to  expand  an  amount  sufficient  to  bind  in  the  hole  reamed. 

In  Fig.   159  is  shown  a  three-flute  chucking  reamer.     These 


FIG.  159. 

reamers  have  the  shanks  and  fluted  portion  ground  cylindrically 
true  and  are  specially  adapted  to  the  reaming  of  deep  cored 
holes. 

The  shell  reamers,  Figs.  160  and  161,  are  chucking  or  rose 

i 


FIG.   1 60. 


FIG.   l6i. 


reamer  heads,  having  round  central  tapered  holes,  the  taper  used 
being  J/£  of  an  inch  per  foot  for  the  reception  of  the  arbor  shown 
in  Fig.  162.  A  rectangular  slot  or  key- way  is  milled  across  the 


FIG.  162. 

shank  end  to  receive  the  cross  key  of  the  arbor ;  several  sizes  of 
reamers  fitting  each  size  of  shank.  The  first  cost  of  a  set  of  shell 
reamers  and  arbors  is  but  little  less  than  that  of  a  set  of  regular 
rose  or  fluted  chucking  reamers. 


I2O  MODERN    MACHINE    SHOP   TOOLS. 

In  Fig.  163  is  illustrated  a  taper  hand  reamef.  The  reamer 
shown  is  a  standard  taper  pin  reamer  having  a  taper  of  l/\.  inch 
per  foot.  The  Morse  taper  reamers  of  approximately  J/£  inch  per 
foot  and  the  Brown  &  Sharpe  standard  taper  reamers  of  3/2  inch 
per  foot  are  in  all  respects  similar  to  the  taper  pin  reamer  shown. 

When  a  solid  reamer,  through  wear,  falls  below  standard 
size  an  amount  greater  than  the  allowable  limit  of  error,  it  can 
be  brought  up  to  standard  size  again  only  by  drawing  the  temper, 
upsetting  the  teeth  by  driving  against  their  front  faces,  retemper- 
ing  and  regrinding.  This  is  an  expensive  and  unsatisfactory 
operation.  It  will  usually  be  found  best  to  grind  it  to  about  .005 
tinder  size  and  use  it  for  a  sizing  reamer.  In  some  cases  it  is 
possible  to  grind  them  to  the  next  thirty-second  or  even  sixteenth 
size  smaller.  This  makes  the  teeth  wide  on  top ;  but  if  the  clear- 
ance is  properly  ground,  the  reamer  will  work  well.  In  such  cases, 


FIG.  163. 

care  must  be  taken  to  obliterate  the  original  size  stamp,  and  re- 
place with  a  new  one  to  avoid  errors. 

It  must  not  be  inferred  that  a  properly  made  solid  reamer  falls 
quickly  below  size  when  properly  used.  Its  life  as  a  standard  tool 
depends  upon  the  hardness  of  the  metal  reamed  and  the  amount 
of  cut  it  is  required  to  take.  It  must  be  remembered  that  the 
standard  reamer  is  a  finishing  tool,  and  must,  as  such,  be  capable 
of  reaming  a  great  many  holes  to  practically  the  same  diameter. 
To  accomplish  this  the  cut  must  be  very  light,  never  exceeding 
1-64  of  an  inch,  and  preferably  not  more  than  .005  to  .01  of  an 
inch.  When  great  uniformity  is  required,  a  sizing  reamer  .005  to 
.007  of  an  inch  under  size,  usually  operated  by  power,  is  first 
passed  through  the  hole.  This  leaves  a  true  hole  and  equal  cut 
for  the  finishing  hand  reamer. 

There  are  numerous  adjustable  reamers  on  the  market.  Fig. 
164  shows  the  Cleveland  common-sense  expansive  reamer  in 
which  a  screw  in  the  point  forces  a  tapered  plug  into  the  tapered 
hole  in  the  center  of  the  tool  which  expands  the  teeth,  the  slots 
parallel  to  the  teeth  and  extending  through  to  the  bore,  allowing 
the  necessary  amount  of  spring.  It  is  evident  that  the  teeth  ex- 


REAMERS. 


121 


pand  most  at  the  center,  but  as  the  amount  of  expansion  necessary 
to  preserve  standard  diameter  is  very  small,  this  will  have  little 
effect  on  the  working  of  the  tool.  The  cylindrical  portion  of  the 
point  is  called  the  "guide"  or  the  "pilot"  point,  and  is  usually 
ground  .005  to  .007  of  an  inch  under  size,  which  of  course  limits 
the  amount  of  stock  left  for  finishing.  This  reamer  is  made  from 
y§  of  an  inch  to  2.^/2.  inches  in  diameter,  and  is  strictly  an  ex- 
pansive reamer. 

A  form  of  Morse  adjustable  blade  reamer  is  illustrated  in  Fig. 
165.    It  consists  of  a  suitable  number  of  blades  or  chasers,  fitting 


FIG.  164. 


FIG.  165. 


FIG.  1 66. 

milled  slots  and  abutting  against  a  ground  tapered  plug  in  the 
center  of  the  head.,  the  end  of  which  is  threaded  into  the  shank. 
By  screwing  the  plug  in,  the  blades  are  forced  out  the  required 
amount,  and  when  adjusted,  the  dished-head  nut  engages  the 
beveled  ends  of  the  blades,  holding  them  firmly  in  position.  These 
reamers  have  an  adjustment  of  about  1-32  of  an  inch,  and  are 
regularly  made  in  sizes  from  y^  of  an  inch  to  2  inches. 

Fig.  1 66  illustrates  an  adjustable  reamer  in  which  the  blades, 
which  are  unequally  spaced,  are  fitted  in  radially  tapered  grooves. 
Cupped  collars  engage  the  beveled  ends  of  the  blades,  holding 
them  firmly  in  position.  The  adjustment  is  made  by  slacking  the 
upper  collar  and  forcing  the  blades  toward  the  shank  by  the 


122 


MODERN    MACHINE    SHOP   TOOLS. 


lower  collar.  A  reamer  of  this  class  with  steep  taper  to  the 
bottom  of  the  grooves  and  long  threaded  portions  can  be  adjusted 
for  several  sizes.  This,  however,  is  not  considered  good  practice, 
the  adjustment  being  simply  to  maintain  one  size.  This  adjust- 
ment, however,  is  great  enough  to  allow  for  several  regrindings. 

Those  classes  of  adjustable  blade  reamers  in  which  each 
blade  is  set  out  independently  should  be  reground  after  each  ad- 
justment, as  it  is  almost  impossible  to  set  the  blades  out  equally. 

In  using  the  reamer  it  should  be  turned  continually  forward, 
both  on  the  advance  and  on  the  withdrawal.  Turning  it  backward 
while  in  the  work  is  quite  apt  to  injure  the  tool,  due  largely  to 
small  particles  of  cuttings  lodging  between  the  clearance  sur- 
faces and  the  wall  of  the  hole.  In  hand  reaming  the  tool  can 
usually  be  passed  through  the  work.  Oil  should  be  used  freely 
in  reaming  steel  or  wrought  iron.  Cast  iron  and  brass  are  usually 
reamed  dry.  A  small  amount  of  oil  will,-  however,  frequently 
improve  the  quality  of  the  work  in  these  metals. 

The  preparation  of  the  holes  for  taper  reaming  is  of  great  im- 
portance. As  a  reamer  should  not  remove  all  the  metal  that 
would  be  left  if  a  drill  the  size  of  the  point  of  the  reamer  were 
passed  through  the  work,  several  drills  of  different  diameters 
may  be  used,  producing  a  stepped  hole,  as  shown  in  Fig.  167.  If 


FIG.  167. 

the  work  is  done  in  a  lathe,  the  taper  attachment  or  compound 
rest  can  be  advantageously  used,  using  a  boring  tool  to  enlarge 
the  drilled  hole.  If  the  lathe  has  neither  of  these  attachments, 
the  hole  can  be  stepped  out,  as  in  Fig.  167,  with  the  boring  tool. 
A  roughing  reamer,  Fig.  168,  is  well  suited  to  the  preparation  of 
a  hole  to  be  taper  reamed. 


FIG.  1 68. 


REAMERS. 


123 


A  simple  form  of  reamer  shown  in  Fig.  169  will  frequently 
obviate  the  expense  of  a  special  reamer  when  only  a  few  holes  are 
to  be  sized.  The  tool  can  be  made  at  slight  expense,  and  when 
carefully  constructed  will  produce  very  good  results. 

The  taper  pipe  reamer,  Fig.  170,  is  a  roughing  reamer  of 
standard  pipe  tap  taper  for  sizing  a  drilled  or  bored  hole  before 
tapping  with  pipe  tap. 

The  reamers  used  for  reaming  center  bearings  in  work  to  be 


FIG.   169. 

machined  between  centers  are  shown  in  Fig.  171.  A  is  the  "old 
Hartford"  reamer  with  one  cutting  edge.  It  cannot  be  relied 
upon  to  produce  a  true  conical  hole.  A  "new  Hartford"  center 
reamer  is  shown  at  B.  It  has  three  cutting  edges,  and  will  pro- 
duce a  true  hole.  These  reamers  are  intended  to  follow  a  small 
drilled  center  hole,  and  are  made  with  6o-degree,  72-degree  and 


FIG.  170. 

82-degree  angles,  60  degrees  being  the  standard.  They  are  also- 
made  in  several  sizes  from  y±  to  ^  of  an  inch,  largest  cutting 
diameters.  A  form  of  combination  center  reamer  and  drill,  in 
which  the  drill  and  reamer  blades  are  held  in  a  suitable  shank,  is 
shown  at  C.  At  D  is  shown  a  combination  center  drill  and 
reamer  that  has  come  into  general  use.  It  is  admirably  adapted 
to  its  work,  being  efficient,  simple  and  inexpensive.  The  drill 
steadies  the  reamer,  which  makes  it  cut  smoother,  and  insures  its 
coming  central  with  the  drilled  hole.  This  is  of  special  value 


124 


MODERN    MACHINE    SHOP   TOOLS. 


when  the  surface  of  the  work  is  uneven.  The  countersink  is  simi- 
lar to  the  center  reamer,  having,  however,  a  greater  number  of 
teeth. 

When  reaming  either  taper  or  parallel  in  a  lathe,  the  work 
rotating  and  the  reamer  held  against  the  dead  center,  true  work 
must  not  be  expected,  if  the  reamer  is  allowed  to  follow  directly 
.after  the  drill,  as  it  is  practically  impossible  to  so  start  a  drill  that 
the  drilled  hole  will  be  exactly  concentric  to  the  axis  of  the  lathe 
spindle.  This  will  cause  the  point  of  the  reamer  to  move  in  a 
small  circle  around  the  center  of  the  rotation,  producing  a  tapered 
instead  of  a  parallel  hole.  If  true  holes  are  required,  the  drill 


used  should  be  enough  smaller  than  the  reamer  to  allow  for  the 
truing  of  the  hole  with  the  boring  tool,  which  will  bring  it  con- 
centric with  the  axis  of  rotation  before  the  reamer  finishes  it  to 
•exact  diameter. 

When  the  reamer  is  used  in  a  drill  press,  correct  results  will 
"be  obtained  only  when  the  hole  reamed  is  exactly  concentric 
with  the  drill  spindle,  otherwise  the  reamer  will  be  held  against 
one  side  of  the  hole,  making  it  elliptical  in  cross-section  at  the 
top.  These  difficulties  in  producing  perfect  reamed  holes  by 
machine-driven  reamers,  compel  the  extensive  use  of  the  hand 
reamer,  the  holes  having  been  previously  sized  with  an  undersize 
reamer. 


CHAPTER   X. 

SCREW    THREADS,    TAPS    AND    DIES. 

As  to  their  uses,  screw  threads  may  be  divided  into  two  classes  ; 
first,  those  used  for  fastenings ;  and  second,  those  used  for  com- 
municating motion.  The  term  "fastenings"  is  applied  to  any 
device  used  to  hold  together  two  or  more  pieces,  either  holding 
them  rigidly  together  or  constraining  any  relative  motion  be- 
tween them.  The  important  position  that  the  screw  thread  holds 
under  this  head  becomes  forcibly  apparent  when  we  consider  a 
machine, -as  a  lathe,  for  example,  and  wonder  how  we  would  man- 
age to  hold  its  numerous  parts  together  without  the  use  of  this 
device.  The  lead  and  cross  feed  screws  in  a  lathe  are  examples  of 
screws  used  to  communicate  motion. 

In  Fig.  172  are  shown  the  three  forms  of  threads  used  for 
fastening. 

In  the  V  thread  the  angle  of  the  sides  with  each  other  is  60 
degrees,  the  top  and  root  of  the  thread  being  sharp. 

The  United  States  standard  thread,  or  as  it  is  often  called, 
the  Sellers  or  the  Franklin  Institute  thread,  is  the  same  as  the- 
V,  with  the  top  cut  off  and  the  root  filled  in.  The  amount  taken 
from  the  top  and  added  to  the  root  is  one-eighth  of  the  height 
of  the  Y  thread,  thus  making  the  United  States  standard  thread 
three-fourths  the  depth  of  the  Y  thread.  The  United  States  stand- 
ard form  of  thread  was  recommended  by  the  Franklin  Institute 
in  1864.  This  system  was  devised  by  Mr.  William  Sellers,  and 
has  become  the  acknowledged  standard  thread  in  the  United 
States.  Its  points  of  superiority  come  from  the  fact  that  it  does 
not  cut  so  deep  into  the  stock  as  does  the  V  thread,  thus  leaving 
a  stronger  root,  while  the  small  amount  cut  from  the  top  and 
bottom  of  the  Y  thread  has  little  strength  value.  It  is  more 
cheaply  produced,  as  threading  tools  with  flattened  points  stand 
up  under  their  work  much  better  than  those  with  sharp  points, 
and  the  filled  root  does  not  form  a  distinct  fracture  line  as  does 
the  sharp  root  of  the  Y  thread.  This  form  of  thread  is  well 
adapted  for  interchangeable  work,  being  used  by  the  leading; 
builders,  and  its  complete  adoption  should  be  urged  by  all. 


126 


MODERN    MACHINE    SHOP    TOOLS. 


In  the  Whitworth*  or  English  standard  thread  the  tops  of  the 
threads  are  rounded  off  and  the  roots  filleted  in.  The  angle  of 
the  sides  with  each  other  is  55  degrees,  and  the  amount  taken 
from  the  top  and  added  to  the  root  is  one-sixth  of  the  height  of 
the  V  thread,  having  sides  at  a  55  degree  angle  with  each  other. 

Each  of  the  threads  shown  in  Fig.  172  is  to  scale  for  stand- 
ard one  and  onej-quarter  inch  bolts,  and  the  dimensions  given  will 
facilitate  comparison. 


V  THREAD 

A/K/K/K 


\  M  V  V 

U.S.  S.  THREAD 


FIG.    172, 


SCREW    THREADS,    TAPS    AND   DIES. 


127 


In  Fig.  173  are  shown  three  forms  of  screw  threads  used  for 
communicating  motion. 

The  pitch  of  the  screw  is  the  distance  it  advances  in  making 
one  revolution;  thus,  the  pitch  of  a  screw  having  eight  threads 
per  inch  is  one-eighth  of  an  inch.  It  is  usual  to  refer  to  the 
number  of  threads  per  inch,  rather  than  to  the  pitch.  For  ex- 
ample, in  Fig.  172  it  is  seven  threads  per  inch,  rather  than  .143 
of  an  inch  pitch. 


SQUARE 
THREAD 


FIG.  173 


128- 


MODERN    MACHINE    SHOP   TOOLS. 


All  screw  threads  may  be  either  right  or  left  handed.  Fig.  174 
illustrates  a  left  hand  screw.  The  left  hand  screw  enters  its  nut 
by  turning  it  counter  clockwise. 

When  a  steep  pitch  is  desired  and  the  diameter  of  the  stock 
would  be  too  small  to  permit  the  use  of  a  single  thread,  two  or 
more  parallel  threads,  dividing  the  pitch  into  two  or  more  parts, 
may  be  used.  Such  are  known  as  double,  triple  and  quadruple 
threads.  A  triple  thread  is  shown  in  Fig.  175,  with  single  thread 
of  same  pitch  shown  dotted. 

The  United  States  standard  admits  of  no  oversizes  and  specifies 

LEFT-HAND  THREAD 


/V\ 


FIG.    174. 


FIG.   175. 


the  number  of  threads  per  inch  for  each  size,  as  well  as  prescrib- 
ing the  form  of  thread.  For  special  work,  however,  it  is  fre- 
quently advisable  to  use  a  different  number  of  threads  per  inch 
from  that  specified  in  this  system,  but  such  will,  of  course,  not 
be  standard,  and  must  always  be  looked  upon  as  special.  The 
following  table  gives  the  principal  diameters  and  corresponding 
numbers  of  threads,  as  determined  in  the  United  States  standard 
system : 

TABLE  OF  SCREW  THREADS. 


Diameter  of  Bolts. 

Dumber  of  Threads 
per  Inch. 

Diameter  of  Bolts. 

Number  of 
Threads  per  Inch. 

i/ 

20 

l# 

7 

ft 

18 

JX 

7 

16 

\$A 

6 

iV 

14 

i% 

6 

M 

13 

i^ 

5 

8 

12 
II 

2 

4 

H 

10 

3 

3^ 

% 

9 

3/12 

3X 

8 

4 

3 

The  screw  threads  with  which  the  machinist  has  to  deal  are 


SCREW   THREADS,   TAPS   AND   DIES. 


I29 


produced  by  cutting  processes,  in  wi  ich  the  thread  is  formed 
from  the  solid  stock.  Cut  threads  are  produced  either  by  means 
of  a  single  pointed  cutting  tool  or  a  ch?«er  used  in  a  lathe,  or  by 
means  of  taps  and  dies.  In  the  first  cas;  the  pitch  of  the  screw 
being  cut  is  dependent  on  the  lead  screw  01  the  lathe,  while  in  the 
latter  case  the  pitch  is  dependent  on  the  le  i  of  the  tap  or  die. 
Screws  used  for  communicating  motion,  or  where  accuracy  is 
desired,  are  cut  in  the  lathe,  while  there  used  for  fastenings  are 
usually  cut  by  the  other  method. 

The  tap  is  a  tool  used  to  produce  internal  threads,  and  the 


Taper. 


Bottoming. 


die  is  a  tool  used  in  cutting  the  external  threads.  Hand  taps  and 
dies  are  those  intended  to  be  used  by  hand,  while  machine  taps 
and  dies  are  those  operated  by  power  in  a  machine. 

The  hand  tap  is  shown  in  Fig.  176.  It  should  be  made  of  a 
high  grade  steel,  and  of  a  temper  specially  suited  to  the  severe 
work  it  is  called  upon  to  perform.  It  is  provided  with  a  round 


I3O  MODERN    MACHINE    SHOP    TOOLS. 

shank,  with  milled  square  to  receive  the  tap  wrench.  This  shank 
is  frequently  turned  to  the  exact  diameter  of  the  root  of  the  thread, 
and  used  to  gauge  the  final  settings  of  the  single  pointed  thread- 
ing tool,  with  which  the  thread  of  the  tap  is  finished,  it  having 
been  previously  roughed  down  with  a  chaser.  This  work  is  done 
in  a 'lathe  having  an  accurate  lead  screw,  the  accuracy  of  the  tap 
depending  largely  upon  this  screw. 

Hand  taps  are  made  in  sets,  three  taps  comprising  what  is 
known  as  a  tap  set.  These  are  called  the  taper,  plug  and  bottom- 
ing, as  shown  in  Fig.  176.  As  manufactured  by  the  Pratt  & 
Whitney  Company,  the  only  difference  between  these  taps  is  in 
the  form  of  the  point.  They  all  have  the  same  thread  parallel  at 
the  root,  and  if  passed  entirely  through  the  work  will  produce 
similar  threads.  The  taper  tap  is  parallel  on  the  point  for  a  dis- 
tance equal  to  one-fourth  the  diameter  of  the  tap.  This  point  is 
made  the  diameter  of  the  roots  of  the  teeth,  which  is  the  correct 
size  of  the  hole  to  be  tapped  in  order  to  produce  a  full  thread. 
The  teeth  at  the  shank  end  are  parallel  for  a  length  equal  to  the 
diameter  of  the  tap,  and  the  balance  of  the  teeth  are  tapered  to 
the  parallel  portion  at  point.  This  gives  a  number  of  teeth  be- 
tween which  the  cutting  duty  in  forming  a  full  thread  is  divided. 

The  taper  taps  manufactured  by  some  makers  have  teeth,  in 
which  the  root  diameter  is-  small  at  the  point,  increasing  on  a 
uniform  taper  to  the  parallel  portion  near  the  shank  end,  and  thus 
dividing  the  taper  between  the  top  and  root  of  the  teeth. 

In  the  plug  tap  the  first  three  teeth  are  tapered  off,  as  shown, 
while  in  the  bottoming  tap  the  teeth  extend  full  to  the  point.  The 
fractional  teeth  at  the  point,  which  would  be  very  apt  to  break, 
are  ground  away. 

The  taper  tap  is  best  suited  to  the  starting  of  a  thread,  but 
unless  the  hole  passes  clear  through,  a  complete  thread  will  not 
be  formed.  The  plug  tap  makes  a  full  thread  nearly  to  the  bot- 
tom of  a  hole,  which  may  be  finished  to  the  very  bottom  with  the 
bottoming  tap.  The  bottoming  tap  should  be  used,  however, 
only  to  finish  out  the  thread,  as  practically  all  the  cutting  is  done 
by  the  four  point  teeth,  which  severely  taxes  their  strength.  When 
possible,  it  is  best  to  drill  the  holes  sufficiently  deep  to  allow  the 
plug  tap  to  finish  the  required  length  of  thread. 

The  plug  tap  is  best  suited  to  general  work,  but  requires  greater 
care  in  starting  it  axially  true  with  the  hole  than  the  taper  tap. 
Machine  taps  are  usually  made  of  the  plug  pattern,  but  as  they  are 


SCREW    THREADS,    TAPS    AND    DIES.  13! 

held  true  to  the  work,  no  difficulty  is  experienced  in  starting  them 
straight. 

Four  grooves  are  ordinarily  milled  in  the  tap,  thus  forming 
four  sets  of  cutting  edges.  The  form  of  this  groove  varies  some- 
what, but  has  little  effect  on  the  cutting  qualities  of  the  tap.  It  is 
usually  so  formed  as  to  bring  the  cutting  faces  of  the  teeth  on  a 
radial  line,  as  shown  in  Fig.  177,  and  should 
be  only  deep  enough  to  allow  room  for  chips 
and  oil  when  tapping  deep  holes.  If  the 
groove  area  is  made  too  large  the  strength  of 
the  tap  is  seriously  impaired.  It  will  be  notic- 
ed in  Fig.  177  that  the  teeth  are  comparatively 
short,  less  than  one-third  of  the  circumference 
having  teeth.  The  shorter  the  teeth  the  less  FIG.  177. 

will  be  the  frictional  resistance  and  the  weaker 
will  be  the  tooth.     As  tap  teeth  are  shortened  by  grinding  from 
the  front  face,  the  teeth  must  not  be  made  too  short  when  new. 

Hand  taps  and  all  others  that  are  backed  out  of  holes  tapped 
are  not  given  thread  clearance.  As  standard  taps  do  not  admit  of 
oversizes,  a  relieved  thread  tap  would,  if  standard  when  new,  fall 
below  proper  diameter  when  ground  on  the  front  faces  in  sharpen- 
ing. A  tap  having  relieved  teeth  will,  when  backed  out  of  the 
thread  it  is  cutting,  allow  the  cuttings  to  wedge  between  thread 
and  teeth,  seriously  injuring  both  work  and  tap.  The  backing 
of  such  a  tap  while  in  the  work  will  frequently  shale  off  the  front 
face  of  the  teeth. 

Taps  that  pass  through  the  work  by  driving  continually  for- 
ward, as  with  nut  taps,  are  given  relieved  teeth ;  they  cut  freer 
and  there  is  less  friction  between  tap  and  thread,  but  should  not 
be  turned  backward  in  the  thread.  The  relief  on  these  teeth  is 
produced  with  uniformity  and  rapidity  on  machines  specially  de- 
signed for  this  purpose. 

Standard  taps  are  made  from  one  to  f*ve  one-thousandths  of  an 
inch  oversize  to  allow  for  the  wear  on  the  top  of  the  teeth.  This 
means  that  a  little  less  than  the  one-eighth  is  taken  from  the  top 
of  the  teeth ;  the  root  diameter  and  sides  of  the  teeth  being  cor- 
rect, this  does  not  affect  the  fit  of  the  thread. 

In  Fig.  178  is  shown  a  pulley  tap  used  largely  for  tapping  the 
holes  for  set  screws  in  pulley  hubs,  a  hole  being  drilled  in  the  rim 
sufficiently  large  to  allow  the  tap  and  shank  to  pass  through.  It 
is  a  regular  plug  tap  with  a  long  shank ;  the  diameter  of  the  shank 


132 


MODERN    MACHINE    SHOP    TOOLS. 


is  the  same  as  the  diameter  of  the  tap.  It  may  be  had  with  any 
reasonable  length  of  shank,  and  will  be  found  a  very  convenient 
tool  for  tapping  holes  in  inaccessible  places. 

The  stay-bolt  tap,  as  shown  in  Fig.  179,  is  a  combined  reamer 
and  tap,  used  by  boiler  makers  for  reaming  and  tapping  the  holes 
for  stay-bolts.  The  taps  are  made  long,  as  the  plates  are  often 
widely  separated,  and  must  be  tapped  together,  as  otherwise  the 
stay-bolts  will  not  enter  the  second  plate  without  springing  the 
plates  a  fraction  of  the  pitch.  These  taps  are  sometimes  made 
as  long  as  five  feet.  They  run  from  three-quarters  to  one  and  one- 
half  inches  in  diameter. 

A  hob,  or  master  tap,  is  one  used  for  cutting  the  threads  in 
dies.  Fig.  180  shows  a  hob  for  cutting 
pipe  dies. 

The  pipe  tap  shown  in  Fig.  181  has 
full  teeth  to  the  point,  the  standard  pipe 
taper  being  three-quarters  of  an  inch  per 
foot.  The  following  table  gives  the 
number  of  threads  per  inch  and  tap  drills 
for  standard  pipe  taps : 


1 

omi 

< j 


FIG.    178. 


FIG.   179. 


FIG.   I  So. 


SfK::\V    T11RKADS,    TAPS    AXU    DIES. 


133 


Diameter  of  Pipe.                 Number  of  Threads. 

Tap  Drill. 

,x 

27 

H 

X 

18 

ft 

f8 

18 

X 

14 
14 

1 

I 

IZi/ 

JH 

lh 

"if 

ij| 

2   ~ 

II^o 

2A 

2M 

8 

2lr 

3 

8 

sX 

3x  •> 

8 

3lff 

4~ 

8 

4A 

In  case  a  pipe  reamer  is  not  used  for  sizing  ahead  of  the  tap 
the  holes  may  be  drilled  1-64  inch  larger  for  the  small  sizes  and 
1-32  inch  for  the  large  sizes. 

Fig.  182  shows  a  machine  or  nut  tap.  It  is  provided  with  a 
long  easy  taper  on  the  threaded  portion  and  a  long  shank  some- 
what smaller  in  diameter  than  the  root  of  the  thread. 

A  combination  drill  and  pipe  tap,  shown  in  Fig.  183,  is  in  quite 
general  use.  It  is  a  valuable  tool  for  drilling  and  tapping  gas 
and  water  pipes  under  pressure. 

A  collapsing  tap  is  one  in  which  the  teeth  or  chasers,  after  cut- 
ting the.  thread,  are  carried  toward  the  center  enough  to  allow 
them  to  clear  the  threads  so  that  the  tap  can  be  removed  without 
backing.  This  not  only  saves  time,  but  the  wear  on  the  teeth 
incident  to  backing  them  out  of  the  threaded  hole.  A  form  of  col- 
lapsing tap  manufactured  by  the  Geometric  Drill  Company  is 
shown  in  Fig.  184. 

The  mechanism  is  such  that  when  the  two  side  stops  come  in 
contact  witL  the  work  the  lead  or  draw  of  the  tap  releases  a  clutch 
in  the  head  which  unlocks  the  mechanism  and  the  chasers  are  in- 
stantly collapsed.  The  setting  of  the  stops  determines  the  depth  of 
the  threaded  hole.  The  chasers  are  then  expanded  again  and 
locked  in  position  for  the  next  operation  by  means  of  the  handle 
shown  on  the  body  of  the  tap.  A  graduated  adjustment  provides 
for  slight  variations  in  the  diameter  of  the  tap. 

The  advantages  of  the  collapsing  tap  over  the  solid  lies  in  the 
saving  of  time  due  to  being  able  to  allow  the  machine  to  run 
continuously  forward,  thus  saving  the  time  required  with  the 
solid  tap  to  back  out.  The  backing  out  not  only  injures  the  tap 


134 


MODERN    MACHINE    SHOP    TOOLS. 


but  is  quite  apt  to  injure  the  thread.     Again,  the  possibility  of 
changing  slightly  the  diameter  of  the  tap  is  frequently  of  value. 
A  limited  number  of  different  sizes  may  be 
tapped  with  each  size  of  head  by  substitut- 
ing different  sets  of  chasers. 

Taps  are  tempered  hard  and  are  conse- 
quently brittle.  They  give  no  warning  before 
they  break,  therefore  care  and  judgment 
must  be  exercised  in  their  use.  In  using 
hand  taps,  a  wrench  which  fits  closely  the 
square  on  the  shank,  and  having  opposite 
handles  of  equal  length,  should  be-  used. 
The  pull  on  the  handles  should  be  uniform 
and  equal.  This  produces  a  torsional  strain 
in  the  tap,  which,  if  working  under  proper 
conditions,  it  will  safely  resist.  Any  excess 
of  pressure  on  one  handle  will  produce  a 
transverse  strain  which  endangers  the  tap. 


FIG.  182 


FIG.   183. 


FIG.   184. 


SCREW    THREADS,    TAPS    AND    DIES.  135 

It  frequently  is  necessary  from  the  nature  of  the  work  to  use 
a  single  handle.  In  such  cases  the  operator  must  grasp  the  head 
of  the  tap  and  wrench  with  his  left  hand  and  balance  the  trans- 
verse moment  of  the  p\ill  at  the  end  of  the  handle,  allowing  only 
the  turning  effort  to  be  received  by  the  tap. 

In  tapping  full  threads  in  tool  steel  great  care  must  be  exer- 
cised, especially  if  the  stock  is  not  thoroughly  annealed.  If  much 
of  this  work  is  to  be  done  two  taps  should  be  used,  the  first  one 
through  removing  only  a  part  of  the  stock,  and  the  second  finish- 
ing. In  tapping  double  threads,  two,  or  even  three  taps,  should 
be  used.  This  becomes  necessary  from  the  fact  that  with  a  double 
thread  twice  the  amount  of  stock  must  be  removed  per  revolution 
of  the  tap  as  with  a  single  thread  of  the  same  depth.  Taps  for 
square  threads  should  also  be  used  in  pairs,  unless  made  extra 
long  with  a  long  tapered  portion. 

When  a  thread  is  to  be  tapped  at  right  angles  to  the  surface, 


FIG.   185. 

do  not  depend  on  the  taps  following  the  drilled  hole,  but  in  start- 
ing test  the  angle  by  squaring  to  the  shank  of  the  tap.  A  tap 
started  crooked  must  be  squared  up  while  the  first  two  or  three 
threads  are  being  cut ;  an  attempt  to  square  it  later  may  result  dis- 
astrously to  the  tap,  and  will  produce  a  threaded  hole  enlarged  at 
the  opening. 

Dies  may  be  divided  into  two  general  classes ;  the  first  should 
include  all  dies  requiring  to  be  passed  over  the  work  several  limes 
in  the  production  of  a  finished  thread ;  the  second,  those  that  pro- 
duce a  finished  thread  at  once  over. 

The  first  class,  example  of  which  is  shown  in  Fig.  185,  con- 
sists of  a  stock  in  which  cutting  dies  are  held.  These  dies  are 
capable  of  sufficient  separation  to  enable  them  to  be  passed  over 
the  work  upon  which  the  thread  is  to  be  cut.  By  means  of  a  set 
screw  or  threaded  handle  the  dies  may  be  closed  an  amount  suf- 
ficient to  make  them  cut  a  full  thread. 


136 


MODERN    MACHINE    SHOP    TOOLS. 


In  the  manufacture  of  these  dies  they  are  threaded  with  a  hob 
tap,  the  diameter  of  which  is  twice  the  depth  of  the  thread  greater 
than  the  diameter  of  the  work  the  die  is  to  be  used  upon.  This 
makes  a  die  with  teeth,  the  tops  of  which  fit  the  work  when  the 
thread  is  started.  This  is  shown  in  Fig.  186.  It  greatly  facilitates 
the  starting  of  a  true  thread.  The  conditions  at  the  finishing  of 
the  thread  are  shown  in  Fig.  187,  in  which  A  A  are  the  cutting 
edges.  When  the  thread  is  started  these  edges  have  no  clearance, 


FIG.  1 86. 


FIG.    187. 


but  as  the  dies  are  forced  toward  the  center  an  increasing  clear- 
ance is  formed.  This  is  clearly  shown  in  the  figures. 

The  dies  are  chamfered  off  on  the  advancing  side  for  two  or 
three  teeth,  so  that  these  teeth  do  the  most  of  the  cutting,  those 
following  simply  sizing.  If  desired  to  cut  a  full  thread  close  up 
to  a  shoulder  the  die  is  turned  over. 

Under  the  second  class  we  consider  first  the  screw  plate,  shown 
in  Fig.  1 88.  This  is  a  thin  plate  of  tempered  steel,  in  which  a 


FIG.  i 88. 


number  of  holes  of  varying  diameters,  threaded  with  different 
pitches  and  provided  with  opposite  notches  to  form  cutting  edges, 
have  been  produced.  It  is  a  primitive  tool,  suited  only  for  work 
of  small  diameter,  where  correct  threads  are  not  required. 

Dies  of  the  second  class  are  usually  made  adjustable  to  com- 
pensate for  wear.    In  Fig.  189  is  shown  a  form  of  die  largely  used 


SCREW    THREADS.    TAPS    AND    DIES.  137 

ior  small  sizes,  one-sixteenth  to  one-quarter  of  an  inch.  It  is 
given  a  spring  temper  at  C,  and  is  held  in  a  wrought  ring,  not 
shown  in  the  figure.  A  small  set  screw  passing  through  the 
ring  and  engaging  the  notch  shown  in  the  die  edge,  serves  to 
spring  the  die  together,  when  through  wear  it  becomes  over- 
size. 

Fig.  190  illustrates  the  Grant  adjustable  die,  in  which  the  four 
chasers  are  held  in  a  cast-iron  collet  surrounded  by  a  wrought 
ring.  The  chasers  are  beveled  off  on  the  outer  ends,  which  en- 
gage with  corresponding  beveled  grooves  in  the  ring.  By  forc- 
ing the  ring  down,  the  chasers  are  moved  toward  the  center.  The 


FIG.  190. 

amount  of  adjustment  in  this  die  is  one-thirty-second  of  an  inch. 
The  chasers  are  numbered,  with  corresponding  numbers  on  the 
side  of  the  grooves  in  which  they  belong.  This  prevents  the  possi- 
bility of  putting  together  incorrectly  when  the  chasers  have  been 
removed  for  grinding. 

This  die  is  sharpened  by  grinding  back  the  front  face  of  the 
-chasers.  They  should  be  ground  only  a  short  distance  back  of 
the  tooth  root,  so  as  not  to  interfere  with  the  bearing  in  the 
collet. 

In  Fig.  191  is  shown  the  lightning  adjustable  die.  The  stock 
is  bored  out  to  receive  the  two  halves  of  the  die.  The  taper  head 
screws  B  B  fix  the  size  and  the  binding  screws  A  A  A  A  hold  the 


138 


MODERN    MACHINE    SHOP    TOOLS. 


parts  firmly  together.     A  separate  stock  is  provided  with  each 
size  of  die. 

In  Fig.  192  is  shown  a  solid  machine  or  bolt  die.    It  is  made  of 


FIG.   191. 

the  same  form  as  the  solid  pipe  die  and  may  be  used  in  either 
a  hand  or  power  holder. 

The  spring  die  shown  in  Fig.  193  is  for  use  in  a  machine  and 
where  smooth,  accurate  threads  are  desired  should  be  used  in 
pairs,  one  for  roughing  and  one  for  finishing.  A  clamp  collar 
fitted  over  the  end  of  the  die  prevents  its  spreading.  This  form  of 


FIG.  192. 

die  can  be  sharpened  by  passing  a  thin  emery  wheel  through  the 
grooves. 

Self-opening  and  adjustable  dies  are  for  machine  threading 
very  generally  used.  The  advantages  are  the  same  as  for  the 
collapsing  tap.  Fig.  194  illustrates  the  Geometric  Drill  Com- 


SCREW    THREADS,    TAPS    AND    DIES. 


pany's  self-opening  die.  This  tool  is  usually  mounted  in  the 
turret  of  a  chucking  machine  or  screw  machine.  The  chasers  are 
set  up  for  the  cut  by  turning  the  head  until  the  mechanism  locks 


FIG.  193. 

them  into  position.  Pulling  forward  on  the  chasers  unlocks  the 
head  and  a  spring  throws  the  dies  out.  In  operation  the  die  is 
moved  forward  over  the  work  until  the  end  of  the  thread  is 


FIG.    194. 

reached,  when  by  stopping  the  carriage  the  forward  lead  or  draw 
ef  the  die  unlocks  it  and  the  chasers  spring  open. 

By  means  of  the  two  screws  and  graduations  shown  on  the 


I4O  MODERN    MACHINE    SHOP    TOOLS. 

side  of  the  tool  a  micrometer  adjustment,  which  controls  all  the 
•chasers,  is  quickly  made,  thus  making  it  possible  to  make  a  tight 
or  loose  fitting  screw  as  desired.  The  die  head  shown  is  provided 
with  a  roughing  and  finishing  attachment  controlled  by  the  small 
lever  at  the  back.  In  using  this  attachment  the  chasers  are  held 
out  for  the  first  cut  over  about  i-ioo  of  an  inch,  which  is  taken 
at  the  second  cut.  This  is  necessary  only  when  extremely  uniform 
and  accurate  threads  are  required.  The  chasers  may  be  very 
quickly  removed  for  sharpening  or  changing  from  one  size  to 
another. 

For  pipe  threading  opening  dies  are  very  extensively  used. 

The  advancing  edge  of  the  die  chasers  in  all  forms  that  produce 
a  finished  thread  at  one  cut,  is  chamfered  off  for  two  or  three 
teeth,  which  divides  the  cutting  duty  and  facilitates  starting  the 
thread.  The  die  should  not  be  run  bottom  side  up  on  the  work, 
as  in  that  case  the  first  tooth  does  nearly  all  the  cutting  duty. 
Only  in  unusual  cases  is  a  workman  justified  in  this  procedure. 

Oil  should  always  be  used  liberally  on  the  tap  or  die  when  cut- 
ting steel  or  wrought  iron;  a  little  oil  on  the  tap  when  cutting 
cast  iron  or  brass  makes  it  run  easier  and  does  no  injury  to  the 
thread  or  the  tool.  Sperm  or  lard  oil  is  best  for  this  purpose. 

In  threading  steel  or  wrought  iron  by  hand  the  tap  or  die 
should,  after  every  two  or  three  turns  forward,  be  given  a  slight 
turn  back.  This  facilitates  the  removing  of  the  cuttings  and 
allows  the  oil  to  find  its  way  to  the  points  of  the  teeth. 

No  mattef  how  accurately  a  tap  or  die  is  cut  the  hardening 
process  will  distort  it  somewhat.  If  this  distortion  followed  any 
fixed  law,  allowance  could  be  made  in  the  threading  that  would 
offset  this  variation,  but  as  the  distortion  is  variable,  even  when 
the  conditions  are  the  most  uniform  possible,  it  is  difficult  to  make 
allowance  for  it.  As  a  general  thing  the  taps  contract  in  length, 
thus  decreasing  the  pitch,  and  expanding  in  diameter. 

A  die  of  standard  diameter  must  not  be  used  to  thread  stock 
that  is  one-thirty-second  of  an  inch  oversize,  as  the  strain  on  the 
die  parts  is  too  great. 

The  practice  of  rolling  iron  one-thirty-second  of  an  inch  over- 
size is  to  be  condemned  as  the  cause  of  mistakes,  lack  of  inter- 
changeability  and  general  confusion,  at  the  same  time  having  no 
advantages.  It  is  not  practical  to  roll  ordinary  bolt  stock  to  ex- 
act sizes,  yet  the  variation  need  not  be  great  and  can  be  taken  care 
of  by  the  standard  dies. 


SCREW    THREADS,    TAPS    AND   DIES.  14! 

The  speed  at  which  threads  may  be  cut  with  taps  and  dies 
in  power  machines  depends  very  largely  upon  the  character  of 
the  work,  quality  of  the  thread  required  and  the  conditions  under 
which  the  work  is  performed.  Cast  iron  and  brass  can  be 
threaded  at  much  higher  speeds  than  steel.  For  equal  diameters 
fine  pitches  may  be  cut  at  higher  speeds  than  coarse  pitches. 
Smooth,  accurate  threads  require  comparatively  slow  speeds. 
For  rough  work  a  speed  of  from  15  to  20  feet  per  minute  is  satis- 
factory when  the  work  and  cutters  are  flooded  with  good  screw 
cutting  oil.  A  speed  of  10  feet  per  minute  is  quite  fast  enough 
when  smooth,  accurate  threads  must  be  had.  When  the  work 
has  been  heated  up  by  a  preceding  operation  the  speed  for  thread- 
ing cannot  be  as  high  as  if  the  work  was  perfectly  cold.  This  is 
usually  the  case  on  the  screw  machines  where  the  threading  fol- 
lows a  heavy  turning  operation.  As  the  threading  requires  but 
little  time  as  compared  with  the  turning  it  is  common  to  sacrifice 
speed  in  threading  for  higher  efficiency  in  turning,  all  of  which 
tends  toward  truer  and  better  threads. 

To  determine  the  diameter  of  hole  required  to  give  a  full 
thread,  caliper  the  root  diameter  of  the"  tap,  the  point  of  the  taper 
tap,  or  consult  a  table  of  tap  drills.  The  number  of  threads  per 
inch  is  always  plainly  stamped  on  the  tap  or  die.  Remember  that 
United  States  standard  for  five-eighths  of  an  inch  is  n,  not  10, 
and  for  half  an  inch  is  13,  not  12  threads  per  inch.  Always  keep 
die  and  tap  threads  sharp  by  grinding  from  the  front  faces  of  the 
teeth.  When  dull  they  jam  rather  than  cut  the  stock  and  require 
excessive  power  to  operate  them. 


CHAPTER   XL 

DRILL  AND  TAP   HOLDERS. 

Drivers  adapted  to  the  proper  holding  of  drills  and  taps  while 
in  use  are  quite  essential  to  their  long  life.  Very  frequently  the 
shank  end  of  these  tools  gives  out  while  the  cutting  end  remains 
in  good  condition.  This  usually  comes  from  not  having  the 
proper  holders  in  which  to  drive  them,  but  very  frequently 
through  the  sheer  carelessness  of  the  operator. 

A  mechanic  is  always  annoyed  when  he  finds  the  drill  he 
wishes  to  use  with  the  shank  mutilated  and  the  tang  twisted. 
Workmen  cannot  be  blamed  for  not  using  what  their  employers 
will  not  furnish,  yet  very  frequently  they  will  not  use  them,  or 
rather  use  them  properly  when  they  are  provided.  A  dog  tight- 
ened onto  the  shank  of  a  taper  shank  drill,  with  a  bar  of  iron 
resting  on  the  shank  and  under  the  tail  of  the  dog,  will  hold 
the  drill  from  rotating  when  held  against  the  tail  center  of  the 
lathe  and  operating  on  chucked  work.  At  least  it  will  hold  it 
part  of  the  time,  the  rest  of  the  time  it  is  slipping  under  the  dog 
screw,  which  plows  up  the  surface  in  fine  shape.  Of  course,  the 
operator  who  would  use  a  taper  shank  drill  in  this  manner  has 
not  the  time  to  smooth  up  the  shank  when  he  finishes  with  the 
drill,  but  leaves  it  for  the  other  fellow  to  do.  The  other  fellow 
is  also  in  a  hurry,  and  jams  the  drill  into  the  taper,  tearing 
the  drill  press  spindle,  growls  because  it  won't  run  true,  and 
finally  when  he  twists  the  tang  off,  declares  that  taper  shank 
drills  are  not  fit  to  drill  lead  with,  and  all  because  the  taper,  due 
to  its  roughed  condition,  not  fitting  properly  in  the  bearing  in 
the  spindle,  threw  the  entire  load  on  the  tang,  which  should  not 
be  expected  to  carry  it. 

Drills  are  usually  held  in  sockets  or  chucks,  depending  on 
whether  they  have  taper  or  straight  shanks.  As  has  already  been 
explained  in  a  preceding  article,  the  shanks  of  taper  shank  drills 
are  turned  to  standard  tapers.  While  great  refinement  is  not 
exercised  in  producing  these  tapers,  they  will  be  found  to  vary 
tmt  little  from  the  exact  taper.  This  is  of  importance  because 
the  socket  shown  in  Fig.  195  should  drive  the  drill  not  by  the 
tang -alone,  but  largely  by  the  friction  between  the  surfaces  of 


DRILL   AND   TAP    HOLDERS. 


143 


the  shank  and  bearing  in  the  socket.  For  the  larger  drill  sizes 
under  each  taper  the  tang  is  the  weakest  part  of  the  drill.  Thus 
the  tang  of  the  No.  I  taper  on  a  one-fourth  inch  drill  will  break 
the  drill  before  it  will  twist,  but  on  a  nine-sixteenths-inch  drill, 
which  has  the  same  tang,  the  tang  will  twist  rather  than  break 
the  drill — that  is,  assuming  that  the  drills  are  driven  by  their 
tangs  alone. 

In  the  socket  the  tapered  bearing  should  not  extend  beyond 


FIG.  195. 


FIG.   196. 


FIG.   197. 


FIG.   198. 


the  bottom  of  the  shank  or  mortise  through  the  shank,  and  the 
slot  should  be  but  slightly  wider  than  the  thickness  of  the  tang. 
This  gives  the  tang  a  good  bearing  well  down  toward  its  base. 
The  slot  must  be  sufficiently  long  to  allowr  the  taper  drift  or 
key,  shown  in  Fig.  198,  to  be  inserted  over  the  end  of  the  tang 
to  force  the  drill  out.  If  the  shank  or  bearing  in  the  socket  is 
jammed,  the  former  will  not  enter  the  bearing  the  proper  depth, 
the  tang  will  catch  on  the  point,  the  frictional  drive  between 
shank  and  bearing  surfaces  will  be  decreased  and  a  twisted  or 


144  MODERN    MACHINE    SHOP    TOOLS. 

broken  tang  will  usually  result.  Frequently,  in  twisting,  the 
tang  will  force  the  drill  out  of  the  socket  an  amount  sufficient  to 
allow  it  to  turn  in  the  bearing,  the  tang  cutting  out  the  sides 
of  the  slot  at  the  bottom  and  thus  ruining  the  socket. 

In  Fig.  199  is  shown  the  new  Cleveland  drill  socket  and  a 
drift.  The  design  of  this  socket  is  to  prevent  the  battering  and 
upsetting  of  the  drill  tangs,  the  drift  seating  squarely  upon  the 
end  of  the  tang  as  shown. 

When  sockets  are  to  be  fitted  to  spindle  or  turret  bearings 
having  other  than  a  Morse  taper,  they  may  be  obtained  with 


FIG.  199. 

rough  shanks,  which  can  be  turned  to  the  desired  size  or  taper. 
Such  a  socket  is  shown  in  Fig.  196. 

When  it  is  desired  to  bush  the  bearing  in  the  drill  spindle  or 
socket  to  a  smaller  size,  the  bushing  or  sleeve  shown  in  Fig.  197 
is  used.  It  is  the  same  as  the  socket,  except  the  shank  is  made 
to  envelop  the  bearing,  thus  decreasing  the  length  of  the  con- 
nection. Sleeves  are  not  as  convenient  as  sockets  when  the 
drill  is  to  be  frequently  removed,  as  it  is  necessary  to  remove 
the  sleeve  before  the  drill  can  be  forced  out.  In  such  cases  it 


DRILL    AND   TAP    HOLDERS. 


145 


is  best  to  bush  the  spindle  bearing  to  the  size  larger  than  the  drill 
taper,  and  then  use  a  socket  for  the  last  reduction. 

In  Fig.  200  is  shown  a  sectional  view  of  the  Cleveland  grip 


FIG.  200. 


socket.  The  object  of  this  socket  is  to  provide  a  stronger 
drive  for  the  drill,  and  thus'  avoid  the  twisting  of  the  tang. 
A  key-way  is  milled  in  the  shank  of  the  drill,  into  which 
the  key  A  of  the  socket  is  forced  by  rotating  the  collar 
B  through  about  one-fourth  of  a  revolution.  The  collar  is 
recessed  as  shown  at  C,  the  recess  being  eccentric  to  the  socket. 
When  the  collar  is  turned  so  that  the  deep  part  of  the  recess  is 
opposite  the  key,  forcing  the  drill  out  crowds  the  key  back  out  of 
way.  When  the  key-way  is  properly  milled,  the  key  so  fits  it  that 
the  drive  is  entirely  removed  from  the  tang.  This  makes  it 
possible  to  use  drills  which  have  had  their  tangs  twisted  off. 
This  collar  and  key,  when  applied  to  the  end  of  the  drill  press 
spindle,  will  hold  the  drill  from  worming  into  the  work  and  pull- 
ing out  of  the  spindle  when  the  point  of  the  drill  strikes  through. 
It  will  also  prevent  boring  bars  from  pulling  out  of  the  bearing 
when  used  for  under-cutting,  a  feature  appreciated  by  those  who 
liave  much  of  this  kind  of  work  to  do. 

When  the  taper  shank  drill  is  to  be  used  in  the  lathe  for  work 
on  chucked  pieces,  the  holder  shown  in  Fig.  201  is  excellently 


FIG.  201. 


adapted.  It  is  virtually  a  sleeve  having  a  long  handle  attached, 
which  may  be  allowed  to  rest  on  the  carriage  of  the  lathe,  the 
shank  end  of  the  drill  being  steadied  on  its  own  center  against 


146 


MODERN    MACHINE    SHOP    TOOLS. 


the  tail  center  of  the  lathe.  Another  holder  for  this  purpose,  Fig-. 
202,  is  made  in  which  a  center  in  the  holder  is  used  rather  than 
the  drill  center.  In  Fig.  203  is  shown  a  sleeve  holder  in  which  the 
sleeve  is  kept  from  rotating  by  means  of  the  two  screws,  which 
have  points  turned  to  fit  the  slot  in  the  sleeve. 

Another  form  of  lathe  socket  is  shown  in  Fig.  204.  By  put- 
ting a  bar  through  the  round  hole  it  may  be  used  between  centers 
and  becomes  similar  to  the  holder  shown  in  Fig.  202.  It  is,  how- 
ever, usually  used  in  the  tail  spindle  bearing,  the  outside  taper 


FIG.   202. 

being  the  same  as  on  the  dead  center.  When  so  used  it  is 
much  safer  than  when  used  between  centers,  as  the  drill  or 
reamer  it  holds  cannot  pull  off  center. 

The  holder  used  for  driving  the  Graham  grooved  shank  drill 
is  shown  in  Fig.  205.  It  is  made  in  four  sizes,  holding  from 
2^2 -inch  drills  down  to  3-32-inch  drills.  By  means  of  reducers, 
one  of  which  is  shown  in  the  figure,  small  drills  may  be  held  in 
the  large  chucks.  These  holders  are  very  compact,  being  but 


FIG.  203. 

little  larger  in  diameter  than  the  common  socket.  As  the  grooves 
in  the  drill  are  cut  parallel  with  each  other,  taper  shank  drills 
may  be  grooved  to  fit  correctly  in  these  holders,  which,  as  with 
the  socket  shown  in  Fig.  200,  makes  a  good  method  for  reclaiming 
drills  that  have  lost  their  tangs. 

The  above  are  all  positive  drive  holders,  which,  in  the  case  of 


DRILL   AND   TAP    HOLDERS. 


147 


sudden  stopping  of  the  drill  will  break  it  if  the  machine  does  not 
stall.  To  overcome  this,  numerous  friction  drive  holders  have 
been  devised,  one  of  the  best  being  shown  in  Fig.  206.  In  this 
holder  the  socket  A  is  held  by  friction  between  the  end  of  the 


FIG.  204. 


FIG.  205. 


FIG.  206. 


148  MODERN    MACHINE    SHOP    TOOLS. 

shank  G  and  the  collar  B.  F  F  are  fiber  washers  between  the 
sliding  surfaces,  which  gives  a  smooth  motion  "when  slipping 
occurs,  and  enables  the  operator  to  more  easily  adjust  the  tool 
to  the  proper  grip.  The  collar  C  forms  a  lock  nut  to  preserve 
adjustment.  The  bushings  E,  which  carry  the  drills,  fit  in  A, 
being  driven  by  two  keys.  In  its  use  the  collar  B  is  adjusted  up 
until  the  friction  will  just  nicely  drive  the  drill.  This  tool,  which 
is  made  in  two  sizes,  is  provided  with  the  necessary  bushings  for 
holding  drills  and  taps  up  to  i^  inches  in  diameter.  Although 
bushings  for  holding  the  ordinary  square  shank  taps  may  be  had, 
the  tap  with  special  shank  as  shown  in  the  figure  is  best  adapted  to 
use  in  this  holder.  In  machine  tapping,  and  especially  where 
more  than  one  size  of  drill  is  to  be  used,  much  time  may  be  saved 
by  the  use  of  this  holder.  Take,  for  example,  the  drilling  and  tap- 
ping of  engine  boxes,  where  two  drills  are  used,  one  the  diameter 
of  the  stud  through  the  cap,  and  the  other  the  tapping  size  for 
the  stud.  Each  drill  is  placed  in  a  holder,  E.  The  changes  from 
stud  drill  or  tap  drill  and  to  tap  are  made  by  slipping  out  the 
one  holder  and  putting  in  another,  all  of  which  may  be  done  with- 
out stopping  the  spindle.  , 

Another  form  of  friction  tap  holder  is 'shown  in  Fig.  207.  In 
this  holder  the  upper  half  of  the  clutch  is  keyed  to  the  shank, 
the  lower  half  turning  free  on  the  end  of  the  shank.  The  jaws 
of  the  clutch  are  beveled  on  their  edges,  the  spring,  which  is 
readily  adjusted  for  tension,  holding  the  halves  in  contact.  When 
the  drive  on  the  tap  becomes  too  heavy,  the  beveled  edges  force 
the  clutch  halves  apart,  thus  allowing  the  machine  spindle  to 
rotate  without  turning  the  tap. 

The  frictional  drive  tap  holders  shown  in  Figs.  206  and  207 
require  a  reversing  spindle  machine  in  which  to  operate  them.  In 
Fig.  208  is  shown  the  "Star"  tapping  attachment  which  contains 
a  reversing  mechanism,  thus  adapting  it  to  tapping  work  on  ma- 
chines without  reversible  spindle.  As  with  the  others  it  is  pro- 
vided with  an  adjustable  friction  drive  which  can  be  adjusted  to 
the  required  tension  to  drive  any  size  of  tap  the  tool  will  operate. 

In  its  operation.the  body  of  the  tool  is  held  from  rotating  by 
securing  the  chain  shown  to  some  fixed  part  of  the  drilling  ma- 
chine. In  driving  the  tap  forward  the  upper  spindle,  which  is 
independent  of  the  lower,  is  engaged  with  the  lower  by  allowing 
the  weight  of  the  body  to  engage  the  clutch,  which  is  keyed  to 
the  upper  spindle,  to  lock  with  the  lower.  The  upper  bevel  gear 


DRILL   AND    TAP    HOLDERS. 


149 


runs  idle  on  the  upper  spindle.  When  the  tap  has  passed  through 
the  work  or  bottomed  as  the  case  may  be,  raising  the  drill- 
ing spindle  first  disengages  the  clutch  from  the  lower  spindle, 
and  then  clutches  it  with  the  upper  gear,  thus  driving  the  lower 
spindle  through  the  bevel  gears  in  the  reverse  direction  at  an  in- 
creased velocity  due  to  the  increased  ratio  in  the  gearing.  When 
a  number  of  holes  are  to  be  tapped  to  the  same  depth  the  stop 


FIG.  207. 


FIG.  208. 


FIG.   209. 


shown  is  used.  When  this  stop  comes  in  contact  with  the  surface 
of  the  work,  the  body  of  the  tool  stops  and  the  tap  and  its  spindle 
draws  away  from  and  disengages  the  clutch.  A  slight  upward 
movement  of  the  driving  spindle  engages  the  gears  and  the  tap 
is  backed  out. 

The  ''Presto"  drill  chuck,  Fig.  209,  is  a  positive  driven  holder 
provided  with  an  assortment  of  drill  sleeves  which  may  be  se- 


MODERN    MACHINE    SHOP    TOOLS. 


cured  in  the  holder  without  stopping  the  rotation  of  the  machine 
spindle.  The  sleeves  are  driven  by  a  tang  and  held  in  position  by 
two  pins  in  the  body  of  the  holder  which  engage  the  groove 
shown  in  the  sleeve.  The  collar,  which  rotates  upon  the  body  of 
the  holder,  when  down  locks  the  pins  into  the  groove  and  when 
held  up  allows  the  pins  to  throw  back,  releasing  the  sleeve.  A 
marked  saving  in  time  is  effected  by  the  use  of  holders  of  this 
character  on  work  requiring  various  sizes  of  drills  especially  when 
the  drilling  machine  is  provided  with  but  one  spindle. 

Straight  shank  drills  must  be  held  in  drill  chucks,  of  which 
there  are  a  large  variety  on  the  market.  In  Figs.  210  and  211  are 
shown  two  well-known  chucks  for  this  purpose.  They  are  exam- 
ples of  the  two  general  classes,  Fig.  210  showing  a  chuck  in 
which  the  jaws  have  a  radial  motion,  and  Fig.  211  one  in  which 


FIG.  210. 


the  radial  motion  is  due  to  another  motion  along  the  axis  of 
the  chuck. 

Chucks  of  the  class  shown  in  Fig.  210  are  made  in  sizes  to 
hold  from  o  to  2  inches,  while  those  of  the  class  shown  in  Fig.  211 
are  not  made  beyond  ^-inch  capacity. 

The  drill  chuck  shown  in  Fig.  212  is  regularly  made  in  two 
sizes  holding  drills  to  J4  inch.  It  consists  of  a  shank,  sleeve  nut 
and  taper  split  bushings.  The  bushings  are  hardened  and  hold 
but  one  size  of  drill,  separate  bushings  being  required  for  each 
size.  The  compactness  of  this  chuck  makes  it  a  very  convenient 
tool  for  light  work.  By  using  a  split  steel  sleeve  parallel  on  the 
outside  and  tapered  to  fit  the  drill  shank  on  the  inside,  taper 
shank  drills  may  be  satisfactorily  held  in  the  parallel  jaws  of  the 
drill  chuck.  In  the  Pratt  chuck,  a  bar  through  the  chuck  has  a 


DRILL    AND    TAP    HOLDERS.  151 

rectangular  hole,  which  receives  the  tang  of  the  taper  shank  drill, 
thus  making  a  positive  drive. 

In  using  drill  chucks,  it  would  be  well  to  bear  in  mind  that  the 
keys  and  spanners  furnished  with  them  will  grip  the  jaws  suffi- 
ciently tight  upon  the  drill  without  the  assistance  of  a  1 2-inch 
monkey  wrench  or  two  feet  of  gas  pipe.  Overstraining  a  chuck 
destroys  its  accuracy.  Always  remove  a  chuck  from  the  spindle 


FIG.  211. 

the  same  as  you  would  a  drill  or  socket — with  the  drift.  Don't 
feel  that  because  it  has  a  large  hub  you  are  expected  to  knock 
it  out  with  a  hammer. 

Before  inserting  the  shank  of  a  drill,  socket  or  chuck  in  its 
bearing,  wipe  both  surfaces  to  free  them  of  oil  and  dirt,  thus 
making  them  hold  better  and  preventing  injury  to  the  surfaces. 


FIG.  212. 

In  using  the  drift,  a  light  upward  blow  on  the  underside  of  the 
outer  end  will  usually  start  the  drill  easier  than  a  heavier  blow 
on  the  end  in  the  direction  of  its  length. 

The  solid  tap  wrench,  an  example  of  which  is  shown  in  Fig. 
213,  is  provided  with  one  or  more  square  holes  to  fit  the  squares 
on  the  end  of  the  taps.  The  principal  objection  to  the  solid  tap 
wrench  is  that  each  hole  will  properly  fit  but  one  size  of  tap 


152 


MODERN    MACHINE    SHOP    TOOLS. 


shank,  thus  requiring  a  number  of  wrenches  to  meet  general  re- 
quirements. When  more  than  one  hole  is  made  in  this  wrench, 
the  handles  become  of  unequal  length  when  using  any  but  the 
central  hole,  which  results  in  an  unbalanced  pressure  on  the 
opposite  sides  of  the  tap,  producing  a  transverse  strain,  in  the 
resistance  of  which  the  tap  is  weak.  Good  judgment  on  the  part 


FIG.  213. 

of  the  operator  will,  however,  enable  him  to  balance  these  pres- 
sures. Again,  the  tendency  is  to  use  these  wrenches  on  taps  the 
squares  of  which  are  too  small  to  properly  fit  in  the  holes,  thus 
rounding  and  twisting  the  tap  squares. 

In    Fig.    214   is    shown    an    adjustable    tap    wrench.      These* 


FIG.  214. 

wrenches  adjust  to  fit  a  wide  range  of  sizes.  Of  the  particular 
wrench  shown,  five  sizes  take  all  taps  from  the  smallest  to  il/2 
inch.  The  dies  forming  the  squares  are  carefully  hardened  and 
fitted  in  the  body  of  the  wrench,  thus  preserving  a  true  square, 


FIG.  215. 

which  fits  nicely  the  square  on  the  tap  to  which  they  should  be 
closely  adjusted. 

The  T-handled  tap  wrench,  Fig.  215,  is  an  excellent  tool 
for  holding  small  and  medium-sized  taps  in  the  tapping  of  holes 
in  inaccessible  places.  It  is  virtually  a  split  chuck  having  four 


DRILL   AND   TAP    HOLDERS.  153 

slots  cut  in  the  shank  which  engage  the  four  corners  of  the  square 
on  the  tap  shank.  It  is  an  excellent  wrench  for  driving  pin 
reamers. 

Frequently  the  nature  of  the  work  prevents  the  use  of  a  tap 
wrench  having  two  handles.  In  such  cases  the  single  handled 
wrench  is  used.  The  handle  is  preferably  attached  to  the  shank 
through  a  ratchet,  which  enables  the  operator  to  take  shorter 
strokes  than  would  be  necessary  with  the  solid  end  wrench.  Some- 
times a  common  monkey  wrench  is  used  for  this  purpose.  It 
should  be  a  good  wrench,  having  square,  true  jaws,  which  should 
be  carefully  tightened  onto  the  tap  shank  each  time  the  wrench 
is  put  on.  In  using  a  single-handle  tap  wrench,  the  workman 
must  steady  the  shank  with  the  left  hand,  so  as  to  offset  the  side 
pull  on  the  tap. 


CHAPTER   XII. 

MANDRELS. 

The  term  mandrel  is  applied  to  that  class  of  tools  upon  which 
work  that  is  to  be  machined  between  centers  is  usually,  held. 
It  is  frequently  called  an  arbor,  although  the  distinction  between 
the  two  may  be  quite  clearly  defined.  A  mandrel  is  designed  to 
carry  work  that  is  to  be  operated  upon  by  a  cutting  tool,  while 
on  the  other  hand  the  arbor  carries  and  drives  a  cutting  tool,  as 
wTith  the  milling  machine  and  saw  arbors. 

Mandrels  may  be  classed  under  two  heads,  solid  and  expand- 
ing. The  solid  mandrel  is  made  slightly  tapering,  in  order  that 
it  may  be  forced  to  a  tight  fit  in  the  bore  of  the  work.  The 
amount  of  this  taper  varies  with  the  class  of  work  the  mandrel 
is  to  be  used  on,  it  being  but  slight  at  the  most. 

A  bar  of  common  round  iron  or  steel  centered  and  turned 
to  the  required  diameter  constitutes  the  mandrel  in.  its  simplest 
form.  Such  a  tool,  as  is  usually  found  in  the  average  jobbing 
shop,  is  shown  in  Fig.  216.  It  is  hardly  worthy  the  name  man- 


FIG.  216. 

drel,  and  although  a  solid  one  might  fairly  come  under  the  ex- 
panding, or  rather  shrinking  class,  as  it  is  brought  down  by 
turning  and  filing  to  fit  the  bore  of  every  new  piece  of  work 
that  comes  along.  It  has  one  quality,  however,  that  can  always  be 
depended  upon,  and  that  is  untruth.  With  mandrels  of  this  class 
accurate  results  cannot  be  expected. 

Since  a  mandrel  must  be  rigid,  it  should  be  as  short  as  the 
nature  of  the  work  will  permit,  and  made  of  as  stiff  a  material 
as  possible.  Its  centers  should  be  carefully  formed,  and  the 
body  finished  cylindrically  true  upon  them.  The  centers,  at 
least,  should  be  tempered  or  case  hardened,  to  prevent  their  wear- 
in  out  of  true.  In  Fig.  217  is  shown  the  correct  construction  for 
the  end  of  a  mandrel.  The  end  for  a  length  about  equal  to  the 


MANDRELS. 


155 


diameter  of  the  tool  is  reduced  slightly  in  diameter  and  provided 
with  a  flat  on  one  side,  against  which  the  screw  of  the  dog  or 
driver  is  set.  As  the  dog  is  very  apt  to  mutilate  somewhat  the 
ends,  this  reduction  in  diameter  is  quite  necessary.  Since  the 
accuracy  of  the  mandrel  depends  so  much  on  its  centers,  it  is 
necessary  to  protect  them  as  much  as  possible  from  injury  while 
forcing  the  mandrel  into  the  bore  of  the  work.  This  is  best 


FIG.  217. 

accomplished  by  recessing  the  ends  around  the  center  bearing  as 
shown  in  the  figure.  The  angle  of  the  bearing  should  be  60  de- 
grees, with  a  small  hole  drilled  at  the  bottom.  The  object  of  this 
drilled  hole  is  to  prevent  strain  being  thrown  onto  the  delicate 
point  of  the  machine  center,  and  to  form  a  small  oil  reservoir  to 
aid  in  lubricating  the  bearing. 

In  Fig.  218  is  shown  a  hardened  and  ground  steel  mandrel. 
These  tools  are  made  for  general  shop  work,  the  length  increas- 
ing with  the  diameter  from  3*4  inches  for  a  %-inch  mandrel  to 
17  inches  for  a  4-inch.  These  lengths  are,  of  course,  arbitrary 


FIG.  218. 

and  may  for  special  uses  be  materially  increased  or  decreased. 
As  manufactured  by  the  several  makers,  these  mandrels  differ 
but  little  in  length  and  details  of  design.  They  should  be  made 
of  a  good  grade  of  tool  steel,  carefully  hardened  with  the  centers 
lapped  true  after  the  hardening,  and  the  body  ground  cylin- 
clrically  true  upon  these  centers,  it  being  rotated  upon  stationary 
or  dead  centers  for  this  last  operation. 

When  the  greatest  possible  accuracy  is  required  it  is  con- 
sidered best  to  make  these  mandrels  of  tough,  unannealed  tool 
steel,  with  the  ends  only  hardened.  This  arises  from  the  fact 


156  MODERN    MACHINE    SHOP    TOOLS. 

that  the  steel  if  hardened  throughout  changes  somewhat  in  form 
and  receives  temper  strains,  which,  although  relieved  in  the  grind- 
ing, does  not  allow  the  tool  to  immediately  take  its  permanent  set. 
For  this  reason  a  mandrel  that  has  been  hardened  throughout 
should  be  first  rough  ground,  leaving  a  small  amount  for  final 
finishing.  This  finishing  should  not  be  done  for  some  time  after 
the  rough  grinding,  thus  allowing  the  tool  to  season  and  to  acquire 
permanent  set.  The  set  will  not  be  appreciably  altered  if  only  a 
very  small  amount  is  left  for  the  final  finish. 

'Hardening  makes  the  mandrel  stiffer  and  less  liable  to  surface 
injury  than  in  the  case  of  the  unhardened  one.  It  is  not,  how- 
ever, for  the  purpose  of  allowing  careless  workmen  to  run  their 
cutting  tools  into  its  surface  with  the  idea  that  it  will  not  be 
injured  thereby.  Cutting  tools  are  usually  made  of  a  higher 
grade  steel  than  the  mandrel,  and  often  tempered  harder,  in  which 
case  the  mandrel  suffers  if  the  tool  comes  in  contact  with  it. 

These  mandrels  are  usually  tapered  about  one-hundredth  of 
an  inch  to  the  foot,  the  diameter  being  exact  at  the  center.  The 
size  is  stamped  on  the  flat  at  the  larger  end.  They  will  fit  holes 
reamed  with  standard  reamers,  although  the  taper  prevents  uni- 
form grip  on  the  work  at  the  two  ends  of  the  bore.  In  forcing 
these  mandrels  into  the  bore,  good  judgment  must  be  exercised,  as 
they  constitute  a  wedge,  which  will  produce  enormous  pressure 
if  forced  too  hard,  resulting  in  bursting  the  work  if  hard  and 
brittle,  or  if  soft  in  permanently  enlarging  the  bore  and  giving  it 
a  taper  corresponding  to  that  of  the  mandrel. 

The  use  of  the  hardened  and  ground  mandrel  does  much 
toward  the  preserving  of  uniformity  in  the  size  of  holes,  in  the 
work  of  shops,  where  these  tools  are  used.  A  hole  only  a  few  thou- 
sandths of  an  inch  under  or  over  size  prevents,  in  the  first  case, 
the  mandrel  from  entering,  and  in  the  latter  allows  it  to  fall 
through.  Its  slight  taper  makes  it  a  good  comparative  gauge  by 
means  of  which  minute  differences  in  diameter  of  bores  may  be 
compared  by  the  relative  distance  to  which  the  mandrel  enters. 

Expansion  mandrels,  while  possessing  the  decided  advantage 
over  the  solid  ones  of  a  parallel  grip  in  the  bore  of  the  work,  have 
too  often  the  disadvantage  of  complication  of  parts,  which  makes 
them  unsuitable  for  the  most  accurate  work,  and  especially  so  after 
they  have  become  somewhat  worn.  These  objections,  however, 
can  hardly  be  said  to  exist  in  the  case  of  the  mandrel  shown  in 
Fig.  219.  This  mandrel  consists  of  a  cast-iron  bushing,  having  a 


MANDRELS. 


157 


tapered  bore,  which  fits  accurately  the  taper  of  the  mandrel.  The 
bushing,  which  is  ground  externally,  parallel  and  to  exact  diam- 
eter, is  split  partly  through  at  two  points,  and  entirely  through  at 
a  third,  thus  allowing  for  a  slight  expansion  when  the  mandrel  is 
driven  in.  Three  bushings  varying  by  sixteenths  for  the  smaller 
and  eighths  for  the  larger  sizes  may  be  used  on  each  size  of  man- 
drel. The  taper  used  is  !/2  mcn  per  foot,  the  bearing  surfaces 
being  accurately  ground.  It  is  evident  that  the  allowable  amount 
of  expansion  is  small,  yet  sufficient  to  grip  firmly  in  an  accurately 


FIG.  219. 

sized  hole.  An  attempt  to  expand  this  bushing  in  an  oversized 
hole  would  result  in  cracking  it ;  a  thing  that  would  happen  before 
the  bushing,  due  to  its  expansion,  would  throw  the  mandrel  ap- 
preciably out  of  true.  The  bushings  are  regularly  listed  from 
Y%  inch  to  3^  inches  in  diameter,  requiring  eleven  mandrels  for 
the  complete  set. 

The  expanding  mandrel,  Fig.  220,  consists  of  a  hardened  and 


FIG.  220. 


ground  mandrel   with  four  splines  milled  at  an  angle  with  the 
axis,  four  jaws  and  a  containing  band  of  seamless  drawn  steel 


158  MODERN    MACHINE    SHOP   TOOLS. 

tubing.  The  jaws  fit  the  slots  in  the  band  nicely  and  are  carefully 
seated  on  the  bottom  of  the  grooves  in  the  mandrel. 

The  outer  edges  are  ground  parallel.  Forcing  the  mandrel 
through  the  jaws  expands  them.  These  tools  are  regularly  made 
in  eleven  sizes,  taking  from  ^4  mcn  to  7  inches.  On  those  running 
between  I  inch  and  2.^/2  inches  two  sets  of  jaws  are  furnished  for 
each  mandrel,  and  above  2.^/2  inches  three  sets. 

The  mandrel  of  Fig.  221  consists  of  three  stepped  jaws,  capa- 
ble of  end  motion  in  three  splines,  which  are  milled  in  the  body 
of  the  mandrel  at  a  considerable  angle  with  the  axis.  The  head 
A,  which  moves  over  a  parallel  portion,  E,  of  the  mandrel  is 
recessed  at  C  to  receive  the  notched  ends  of  the  jaws,  thus 
holding  them  in  the  same  relative  position.  In  operating,  the 
jaws  are  moved  to  the  small  end  of  the  mandrel,  the  work  placed 


A  r 


FIG.  221. 

on  the  proper  step  and  the  mandrel  forced  through,  the  jaws 
expanding  to  the  bore  of  the  work.  This  tool  is  made  in  four 
sizes,  fitting  all  bores  from  ^  to  4  inches. 

When  it  is  necessary  to  face  a  piece  of  work  that  is  being 
driven  on  a  mandrel  close  down  to  the  bore,  the  expanding  types, 
as  shown  above,  have  the  advantage  over  the  solid  mandrel,  since 
the  work  can  be  left  projecting  slightly  over  one  end  of  the  bush 
or  jaws,  which  allows  room  "for  the  cutting  tool  to  pass  over  the 
edge  of  the  bore. 

Frequently  it  becomes  necessary  to  machine  work,  the  bore 
of  which  is  other  than  cylindrical,  on  a  mandrel.  When  the 
cross-section  of  such  bores  is  circular,  a  cone  mandrel  can-  be  used 
to  advantage.  Such  a  tool  is  shown  in  Fig.  222.  It  is  strictly 
a  special  tool,  as  its  range  of  adaptability  is  small.  It  is  necessary 
that  the  faces,  A  A,  of  the  work  be  machined  at  right  angles  to 
the  bore  before  placing  on  the  mandrel,  as  otherwise  the  work 


MANDRELS. 


159 


will  not  be  held  concentric  with  its  axis.  The  coning  bush,  B,  may 
be  shrunk  on,  pinned  or  threaded  to  the  mandrel,  and  C  should  be 
keyed  and  backed  up  with  a  nut.  These  bushes  should  be  turned 
in  place  on  the  mandrel  centers. 

For  mandrels  of  large  diameter  the  form  shown  in  Fig.  223 
is  frequently  used.  Here  the  draw  bolts,  A  A,  two  to  four  in 
number,  take  the  place  of  the  nut  in  the  preceding  figure.  As  be- 


FIG.  222. 


fore,  one  disk  is  secured  to  the  mandrel  and  the  other  keyed  but 
capable  of  motion  over  it. 

In  Fig.  224  is  shown  a  kink  in  mandrels  that  for  some  classes 
of  work  can  be  used  to  advantage.  As  with  all  tools  of  this 
class  it  should  be  reasonably  well  made,  accurately  finished  as  to 
diameter  and  parallel.  A  short  piece  of  round  drill  rod  serves  for 
the  roller  which  lies  in  a  milled  groove  that  is  a  few  thousandths 
of  an  inch  deeper  at  the  back  than  the  diameter  of  the  roller.  In 


FIG.  224. 


.  225. 


operation,  the  first  start  of  the  work  to  turn  wedges  the  roller  be- 
tween the  slot  and  the  wall  of  the  bore,  holding  the  work  firmly 
from  turning.  A  slight  backward  turn  releases  it,  and  the  mandrel 
can  be  slipped  out  without  pounding.  The  bore  of  the  work  must 
fit  the  mandrel  exactly,  as  the  slack  is  all  taken  up  on  one  side, 
which  will  throw  the  work  out  of  true  if  loose.  This  mandrel 
would  not  be  suitable  for  work  on  which  the  pressure  of  the  cut 
was  in  the  direction  of  its  axis,  as  in  most  milling  and  planing  be- 
tween centers. 


l6o  MODERN    MACHINE  'SHOP    TOOLS. 

When  the  bore  of  the  work  is  threaded,  the  mandrel  must  be 
provided  with  a  thread  to  fit  the  bore,  and  a  radial  face,  against 
which  the  work  screws  to  a  stop.  This  is  commonly  known  as 
a  nut  mandrel,  and  in  its  simplest  form  is  shown  in  Fig.  225. 
Work  that  is  to  be  finished  on  this  mandrel  should  at  the  time 
of  threading,  if  possible,  have  one  face  turned  at  right  angles 
to  the  bore,  so  that  it  may  seat  squarely  against  this  face.  This, 
however,  is  not  possible  when  the  work  is  tapped,  as  is  the  case 
with  nuts.  Since,  for  rapidity  of  manipulation,  the  mandrel 
should  not  fit  the  thread  of  the  work  too  closely,  an  untrue 
seat  cocks  the  work,  and  it  is  not  faced  squarely.  The  ball  seat 
face  of  the  mandrel  shown  in  Fig.  226  overcomes  this  difficulty 
very  nicely. 

In  finishing  round,  smooth  machine  parts  on  a  screw  or  nut 
mandrel,  they  usually  tighten  under  the  pressure  of  the  cut  so 
firmly  against  the  face,  that  it  is  difficult  to  remove  them  without 


FIG.  226.  FIG.  227. 

injuring  their  finish.  The  mandrel  shown  in  Fig.  227  is  a  valuable 
tool  on  work  of  this  character.  The  collar  A  forms  the  bearing 
face  F  and  is  keyed  to  the  mandrel,  the  spline  allowing  it  to  slip 
back  when  the  nut  B  is  slacked,  and  thus  relieves  the  pressure 
between  F  and  the  face  of  the  work.  By  using  a  finer  pitch  thread 
in  B  than  the  mandrel  thread,  C,  or  a  left-hand  thread  in  B,  when 
C  is  right  hand,  the  collar  may  be  omitted.  This  makes  a  cheaper 
mandrel,  but  is  not  so  good,  as  the  nut  and  work  lock  so  firmly 
that  considerable  force  is  usually  necessary  to  start  the  former. 
When  the  work  is  to  be  faced  the  threaded  portion  of  the  mandrel 
should  be  somewhat  shorter  than  the  thickness  of  the  work,  thus 
allowing  the  cutting  tool  to  reach  the  tops  of  the  threads  in  the 
bore  without  injuring  the  mandrel  threads. 

A  stub  mandrel  is  one  used  in  the  end  of  a  piece  of  work,  as 
shown,  for  example,  at  A  in  Fig.  228.  These  generally  fit  a  tap- 
ered seat,  and  are  special  in  character. 

Mandrels  will  usually  drive  the  work  by  friction.  If  the  work 
is  large  in. diameter  for  the  size  of  the  bore,  it  should  be  driven, 


MANDRELS. 


161 


If  possible,  from  a  point  near  the  circumference,  independent  of  the 
mandrel.  A  mandrel  the  surface  of  which  has  been  oiled  slightly, 
will  drive  nearly  as  well  as  if  dry ;  and  the  chances  of  abrasion, 
in  case  of  slipping,  with  its  certain  injury  to  tool  and  work, 
materially  decreased. 

Mandrel  center  bearings  are  often  made  too  small  to  wear 
well,  as  the  intense  pressure  between  the  machine  center  and 
the  bearing  prevents  proper  lubrication  and  increases  the  chances 
of  breaking  off  the  center.  A  shallow  trench,  cut  to  the  point 
of  the  machine  center  on  the  top  side,  improves  the  chances 
of  getting  oil  to  the  bearing  and  does  not  injure  the  center,  the 
pressure  on  it  being  generally  from  the  under  side.  When  rotat- 
ing between  rigidly  clamped  centers,  the  slight  expansion  of 


FIG.    228. 


FIG.  229. 


the  mandrel,  due  to  the  heating  of  the  work,  will  frequently 
increase  the  pressure  between  centers  and  bearing  sufficient  to 
force  out  all  lubrication,  and  cause  abrasion  of  the  surfaces, 
which  is  certain  to  ruin  the  bearing.  This  trouble  is  most  likely 
to  occur  when  the  work  is  rotating  at  a  high  rate,  as  for  filing  or 
polishing.  This  bearing  should,  therefore,  be  of  liberal  size  and 
well  lubricated. 

Since  the  value  of  a  mandrel  depends  largely  upon  the  con- 
dition of  its  center  bearings,  it  is  very  important  that  they 
be  carefully  protected  from  injury  in  driving.  Nothing  harder 
than  a  copper  hammer  should  be  used  on  the  mandrel  ends.  A 
babbitt  hammer  or  raw-hide  mallet  is  preferable.  If  these  are 
not  available,  a  block  of  tough  wood,  end  grain,  must  be  used 
under  the  common  hammer.  The  mandrel  block  shown  in  Fig. 


162 


MODERN    MACHINE    SHOP   TOOLS. 


229  forms  a  solid  support  for  the  work  while  the  mandrel  is  being- 
driven  in  or  cut. 

The  best  practice  dispenses  entirely  with  driving  and  presses 
the  mandrel  into  the  bore.  A  press  designed  for  this  purpose 
is  shown  in  Figs.  230  and  231. 

The  smaller  press,  Fig.  230,  is  for  light  work,  handling  man- 
drels up  to  1^2  inch  in  diameter.  It  is  arranged  to  clamp  to  the 
bed  of  the  lathe  or  on  a  bench.  For  the  heavier  work  the  press 
shown  in  Fig.  231  is  suitable.  It  is  mounted  on  its  own  column  and 


FIG.  230. 


FIG.  231. 


provided  with  an  adjustable  knee.  The  plunger  and  lever  are 
counter-weighted  and  a  ratchet  lever  adjustment  provided  on  the 
pinion  shaft.  When  the  lever  is  up  the  pawl  is  disengaged  and  the 
plunger  can  be  quickly  adjusted  to  any  required  height  by  turning- 
the  hand  wheel.  A  lead  pad  on  the  base  of  the  column  prevents  in- 
jury to  the  mandrel  should  it  fall  in  pressing  out.  The  loop  shown 
prevents  the  mandrel  from  falling  on  its  side.  With  these  presses 
mandrels  may  be  forced  squarely  without  injury  to  them  or  the 
work. 


CHAPTER  XIII. 

THE    LATHE. 

That  most  important  of  all  machine  tools,  the  lathe  in  its 
several  forms,  naturally  comes  first  for  our  consideration.  The 
great  variety  of  work  that  can  be  performed  on  the  lathe,  and 
the  efficient  way  in  which  it  is  done,  are  the  conditions  upon 
which  its  importance  depends.  The  young  mechanic,  when  com- 


FIG.  232. 

plete  master  of  the  lathe,  as  used  in  general  work,  will  have 
learned  nearly  all  the  principles  involved  in  the  operating  of  the 
other  classes  of  ordinary  machine  tools. 

For  special  work  the  lathe  is  so  modified  to  meet  the  parti- 
cular conditions  that  its  identity  is  almost  lost.  For  example,  the 
turret  lathe,  the  screw  machine,  the  pipe  threading  machine,  the 
cutting  off  machine  and  even  the  vertical  boring  mill  are  all 


164  MODERN    MACHINE    SHOP    TOOLS. 

modifications  of  the  lathe  in  which  the  principle  of  rotating  the 
work  to  a  stationary  cutting  tool  is  carried  out. 

The  speed,  or  hand  lathe,  an  example  of  which  is  shown  in 
Fig.  232  is  the  simplest  form  of  metal  turning  lathe.  It  is  a 
single  geared  lathe  which  means  that  the  cone  is  secured  to  the 
spindle,  the  number  of  changes  in  spindle  speed  depending  upon 
the  number  of  steps  on  the  cone.  The  tool  rest  is  adjustable 
in  all  directions,  but  not  provided  with  feeds.  These  lathes, 
when  provided  with  foot-power  mechanism,  may  be  driven  by 
the  operator.  They  are,  however,  usually  furnished  with  a  coun- 
tershaft and  driven  from  some  other  source  of  power.  The  hand 
lathe  is  used  for  all  classes  of  turning  operations  in  which  a  hand 
tool  is  used.  They  are  also  used  for  drilling,  filing  and  polish- 
ing rotating  work.  When  used  largely  for  drilling,  the  lever 
operated  .tail  stock  spindle,  as  shown  in  Fig.  233,  is  of  value,  as 


FIG.  233. 

it  provides  for  a  quick  movement  of  the  spindle  and  is  more  sensi- 
tive than  the  wheel  and  screw  feed.  In  the  tail-stock  shown  the 
spindle,  screw  and  hand-wheel  are  mounted  in  a  quill  which  fits 
the  bearing  in  the  body  casting.  A  segment  of  a  gear  pivoted  at 
the  back  of  the  body  casting  engages  a  rack  cut  on  the  quill. 
Turning  the  segment  by  means  of  the  lever  moves  the  quill  and 
spindle.  Locking  the  segment  secures  the  quill,  and  the  ordinary 
screw  feed  can  be  used  independent  of  the  lever. 


THE  LATHE.  165 

The  standard  engine  lathe  as  shown  in  Fig.  234,  and  so  exten- 
sively used  for  general  shop  work,  is  in  the  smaller  and  medium 
sizes  a  double-geared  screw-cutting  lathe.  In  the  larger  sizes 
triple;  or  quadruple  gearing  is  used  instead  of  double,  the  term 
double,  triple  and  quadruple  referring  to  the  number  of  speed 
reductions  in  the  back  gearing.  The  term  self-acting  implies 
that  the  cutting  tool  is  automatically  actuated  in  all  of  its  feeds. 

The  lathe  primarily  consists  of  four  elements ; — bed,  head- 
stock,  tail-stock  and  carriage.  The  bed  is  the  foundation  upon 


FIG.  234. 

which  the  other  elements  operate  over  accurately  planed  and 
fitted  shears.  It  should  be  well  designed,  heavy  and  rigid.  The 
deflection  due  to  its  own  weight  and  the  pressure  of  the  cut  must 
be  within  very  narrow  limits.  The  form  of  shears  used,  on  en- 
gine lathes,  almost  without  exception,  is  shown  in  the  cross  sec- 
tion of  bed,  Fig.  236.  The  head  and  tail-stocks  rest  upon  the 
inside  pair  and  the  carriage  on  the  outer  pair.  This  view  also 
shows  the  cross  section  of  bed  usually  employed.  It  consists 
of  two  parallel  Fs  tied  at  frequent  intervals  by  the  cross  girts 
shown.  Beds,  when  short,  are  supported  on  legs  at  the  ends,  as 
shown  in  Fig.  234,  but  when  the  length  becomes  excessive  and  ma- 


i66 


MODERN    MACHINE   SHOP   TOOLS. 


terial  deflection  due  to  its  own  weight  would  result,  one  or  more 
intermediate  supports  are  introduced. 

The  head-stock  contains  the  mechanism  that  receives  and 
transmits  the  power  through  the  spindle  to  the  work.  Its  im- 
portant features  are  the  retaining  head  and  spindle  bearings, 
spindle,  cone,  feed,  screw  and  back-gearing.  The  retaining  head 
should  be  so  formed  as  to  best  resist  the  heavy  strains  to  which 
it  is  subjected.  It  should  be  properly  fitted  to  the  inner  shears 
and  clamped  in  place.  The  live  spindle  and  spindle  bearings  are 
the  most  important  elements  in  the  lathe,  as  the  accuracy  of  the 
work  produced  depends  very  largely  upon  the  accuracy  of  the 
spindle.  It  should  be  cylindrically  true,  accurately  fitted  in  its 
bearings  and  its  center  of  rotation  exactly  parallel  with  the  shears. 
The  threaded  nose  and  center  bearing  must  be  exactly  concentric 


FIG.  235. 


FIG.  236. 


with  the  bearing  parts  of  the  spindle.  The  cone  should  be  given 
a  nice  bearing  fit  on  the  spindle  and  the  back  gears  properly  cut 
and  pitched.  The  feed  and  screw  cutting  gear  should  be  reliable 
and  powerful.  The  head-stock  of  the  lathe  shown  in  Fig.  234 
illustrates  the  general  form  as  used  in  double  geared  lathes. 

The  live  spindle  bearing  is  usually  made  of  bronze  or  genu- 
ine Babbitt  metal.  When  the  latter  material  is  used  it  is,  after 
being  cast  in  the  casing,  peaned  sufficiently  to  fill  out  any  shrink- 
age as  well  as  to  intensify  the  metal,  after  which  it  is  bored, 
reamed  and  carefully  bedded  by  scraping  to  an  accurate  fit  on 
the  spindle.  The  Babbitt  bearing  as  used  on  the  lathes  by  the 
F.  E.  Reed  Co.  is  shown  in  Fig.  235.  In  order  to  reduce  the 
wear  to  a  minimum  the  spindle  bearings  should  be  large.  Pro- 
visions for  taking  up  the  wear  are,  however,  always  neces- 
sary. The  end  thrust  of  the  spindle  is  usually  taken  at  the  end 
hearing,  an  adjustable  thrust  screw  receiving  the  pressure.  The 


THE  LATHE.  l6/ 

modern  engine  lathe  is  usually  provided  with  a  hollow  spindle, 
the  size  of  the  hole  often  being  as  large  as  the  diameter  of  the 
spindle  will  safely  permit.  This  is  frequently  a  point  of  great 
value  in  working  up  stock  that  will  pass  through  the  spindle. 
All  back-geared  lathes  may  be  run  as  single  geared  lathes  by 
locking  the  cone  with  the  spindle  gear.  The  purpose  of  the  back- 
gear  is  to  reduce  the  speed  of  the  spindle  and  correspondingly 
increase  its  pull.  Thus,  with  a  five  step  cone  running  single 
geared,  five  changes  of  speed  can  be  had,  the  speed  reducing  and 
the  leverage  increasing  as  the  belt  is  shifted  from  the  smaller  to 
the  larger  steps.  If,  for  example,  the  smallest  step  is  6  inches 
and  the  largest  18  inches  in  diameter  and  the  countershaft  cone 
has  steps  of  the  same  diameter,  as  is  commonly  the  case,  then,  if 
the  belt  is  running  on  the  large  step  of  the  spindle  cone,  which 
is  making  say  twenty-five  revolutions  per  minute,  a  shift  to  the 
smallest  step  will  give,  if  the  belt  continues  to  run  at  the  same 
speed,  3  x  25  =  75  revolutions  per  minute,  but  in  shifting  to 
the  small  step  on  the  spindle  cone,  the  belt  goes  to  the  large  step 
of  the  counter  cone,  which,  since  the  counter  runs  at  a  constant 
number  of  revolutions  per  minute,  increases  the  belt  velocity  in 
the  ratio  of  6  to  18,  or  three  times,  and  consequently  the  spindle 
will  revolve  3  x  3  x  25  =  225  times  per  minute.  If  now  the 
"back  gear  is  thrown  in,  five  more  reductions  in  speed  may  be  had. 
In  Fig.  237  is  shown  an  outline  of  the  double  gear  arrangement. 
The  cone,  when  back-gear  is  in,  is  disengaged  from  the  spindle 
gear  D,  which  allows  it  to  rotate  free  on  the  spindle.  Gear  A  of 
6ay  30  teeth  is  secured  to  the  cone,  revolving  with  it.  A  gears  with 
B  of  80  teeth,  B  and  C  rotate  together,  C  of  20  teeth  gears,  with 
D  of  90  teeth,  and  since  D  is  keyed  to  the  spindle  the  latter  is 
driven  by  the  cone  through  the  chain,  A,  B,  C  and  D.  If  we 
assume  as  before  that  the  belt  is  on  step  F  and  the  spindle  makes 
25  revolutions  per  minute,  putting  in  the  back  gear  decreases  the 
rotation  of  the  spindle  by  the  amount  of  the  back  gear  ratio  — 
30-80  x  20-90=1-12,  which  would  give  25X1-12  =  2  1-12 
revolutions  per  minute.  If  on  the  small  step  of  the  cone,  it  would 
be  225  X  1-12=  1 8%  revolutions. 

In  outline,  Fig.  238,  is  shown  the  usual  triple  gear  arrange- 
ment. Let  A,  B,  C,  D,  F,  G  represent  the  same  values  as  in 
Fig.  237.  If  I  and  J  are  thrown  out  by  moving  them  through 
their  bearings  in  the  direction  of  the  arrow,  and  C  thrown  into 
gear  with  D,  we  would  have  the  same  conditions  as  in  Fig.  237. 


1 68 


MODERN    MACHINE   SHOP   TOOLS. 


When  arranged  as  shown  in  the  figure,  however,  H  corresponds 
to  C,  and  I  to  D,  J  rotates  with  I  and  gears  with  the  internal 
gear  on  the  back  of  the  face-plate  and  thus  gives  a  second  geared 
reduction.  The  velocity  ratio  would  then  be  30-80  X  30-60  X 
40-200  =  3-80  or  for  the  25  revolutions  of  the  cone  in  the  former 
example  the  spindle  would  revolve  25  X  3~8o  =  15-16  of  one 
revolution. 

In  large  lathes  performing  very  heavy  duty,  the  application/ 
of  the  power  to  the  circumference  of  the  face:plate  steadies  the 
cut   and  removes   the  excessive   torsional   strain   that   would '  be 
thrown    upon    the    spindle    if    all    the    power    was    transmitted 
through  it. 

The   tail-stock,   or   foot-stock,    as   it   is    frequently   called,   is 
accurately  fitted  to  the  inner  shears.     It  can  be  moved  along  the 


j 


FIG.  237, 


FIG. 


shears  and  clamped  firmly  to  them  at  any  point.  The  function 
of  the  tail-stock  is  to  carry  the  tail  or  dead  spindle.  This  spindle 
fits  its  bearing  closely,  can  be  moved  in  or  out  through  a  con- 
siderable range  and  clamped  in  any  position.  The  axis  of  the 
dead  spindle  extended  should  be  coincident  with  the  axis  of  the 
live  spindle.  The  dead  spindle  is  always  provided  with  a  cross 
adjustment  commonly  called  the  set  over  and  much  used  for 
turning  external  tapers  on  work  held  between  centers,  as  well 
as  for  making  the  close  adjustment  necessary  to  bring  the  center 
exactly  in  line  for  parallel  turning. 

A  form  of  tail  stock  largely  used  in  Europe  is  shown  in  Fig. 
239.     It  is  becoming  quite  popular  among  American  builders. 


THE  LATHE. 


169 


Its  leading  advantage  is  in  its  use  on  a  lathe  having  a  com- 
pound rest,  as  it  allows  the  rest  to  swing  around  parallel  with 
the  shears  and  still  get  in  reasonably  close  to  the  center  when 
the  tail-stock  is  close  up  to  the  carriage.  It  is  commonly  called 
the  "cut-away"  tail-stock. 

The  carriage  is  the  tool  carrying  device  and  stands  next  to  the 
head-stock  in  importance.     It  rides,  as  shown  in  Fig.  240,  on  the 


FIG.  239. 

outer  shears  and  is  gibbed  front  and  back  to  the  outer  under 
faces  directly  below  the  shears.  Gibbing  to  the  inner  under  faces 
and  weighting  the  carriage  have  given  over  to  the  better  practice 
above  referred  to.  The  old  weighted  carriage  in  which  a  heavy 
weight,  suspended  from  the  bottom,  held  it  to  the  shears  precluded 
the  possibility  of  cross  girts  to  stiffen  the  bed  and  increased  the 


FIG.  240. 

wear  between  shears  and  carriage.  The  apron  on  the  front  side 
of  the  carriage  contains  the  feed  mechanism  and,  with  the  ex- 
ception of  the  make  of  lathe  of  which  Fig.  240  shows  the  carriage, 
the  lead  screw  and  lead  nut.  The  details  of  the  apron  vary 
considerably,  all  however,  being  intended  to  accomplish  the  same 
results.  In  general,  motion  is  transmitted  from  the  splined  feed 


I7O  MODERN   MACHINE   SHOP    TOOLS. 

rod  through  a  keyed  sleeve  which  slides  over  the  rod  and  carries 
a  bevel  gear  which  connects  through  a  clutch  and  suitable  train 
of  gears  to  the  pinion  which  engages  the  rack  on  the  under  front 
edge  of  the  top  of  bed.  In  a  similar  manner  the  motion  is  com- 
municated to  the  pinion  on  the  cross-feed  screw.  By  engaging 
either  clutch  the  feed  that  it  controls  will  operate. 

A  suitable  clamp  for  securing  the  carriage  to  the  shears  for 
cross-feed  work  is  always  provided.  The  most  common  method 
is  to  pinch  either  the  front  or  back  gib,  the  square  head  screw 
shown  on  the  top  right-hand  side  of  carriage  in  Fig.  234  being  for 
this  purpose. 

The  slide  rest  which  carries  the  cutting  tool  is  gibbed  to  a 
cross  shear  which  is  exactly  at  right  angles  to  the  spindle.  In  its 
simplest  form  the  slide  rest  is  a  single  piece  carrying  the  tool 
post  or  clamp.  This  forms  the  most  rigid  rest,  it  having  but  the 
one  gibbed  joint.  The  raise  and  fall  rest  is  shown  in  Fig.  241.  It 


FIG.  241.  FIG.  242. 

is  a  form  of  elevating  rest.  In  Fig.  242  is  shown  a  compound 
rest.  This  form,  while  not  as  rigid  as  the  plain  rest,  has  become 
very  popular  among  machinists,  because  of  its  points  of  con- 
venience. It  has  the  regular  automatic  cross-feed  and  the 
auxiliary  feed  which  can  be  operated  at  any  required  angle  with 
the  spindle.  This  latter  feed  for  the  larger  lathes  is  frequently 
made  automatic.  The  manner  in  which  it  is  accomplished  by  the 
Putnam  Machine  Company,  on  lathes  from  22  to  42  inch  swing  is 
shown  in.  Fig.  243.  Here  the  splined  cross-feed  screw  carries  a 
sleeve,  which,  by  means  of  an  eccentric  operated  by  the  handle 
at  the  left,  can  be  clutched  with  one  of  the  four  bevel  gears  that 
transmit  the  motion  to  the  nut. 

The  slide  rest  shown  in  Fig.  244  is  for  use  on  speed  lathes  as 
shown  in  Fig.  232  for  light  turning  work.  It  may  be  clamped 
in  any  desired  position  on  the  bed.  It  is  provided  with  hand 


THE  LATHE. 


171 


feeds  only,  and  as  the  slides  are  mounted  on  a  graduated  base  it 
may  be  set  at  any  desired  angle  for  taper  turning. 

In  all  engine  lathes  the  carriage  is  moved  over  the  shears  by 
means  of  the  lead  screw  or  the  feed  rod  and  their  connections. 
The  former  constitutes  a  positive  drive  without  possibility  of 


FIG.  243. 

slippage,  while  the  latter  is  a  purely  friction  drive.  The  in- 
dependent feed  rod  is  frequently  dispensed  with  in  small  lathes, 
and  the  lead  screw  made  to  do  its  work.  In  such  cases  the  lead 
screw  is  splined  and  the  feed  mechanism  is  driven  from  a  collar 
which  has  a  feather  engaging  the  spline  and  slides  over  the  lead 


FIG.  244. 

screw.     As  the  feed  is  engaged  by  means  of  a  clutch  this  also 
forms  a  frictional  driver. 

The  feed  rod  is  driven  by  belt  and  provided  regularly  with 
three  changes  of  speed.     Since  it  is  frequently  desirable  to  have 


172 


MODERN    MACHINE   SHOP    TOOLS. 


feeds  finer  or  coarser  than  these  three  changes  can  give,  it  is  now 
quite  common  to  provide  either  a  change  gear  connection  with 
the  feed  rod  as  shown  in  Fig.  245  or  provisions  for  connecting  the 
feed  rod  with  the  change  gear  mechanism  of  the  lead  screw  as 


FIG.  245. 

shown  in  Fig.  246.  In  Fig.  245,  by  changing  places  with  gears  A 
and  B;  or  substituting  others  any  desired  speed  of  feed  rod  C  can 
be  obtained.  In  Fig.  246  when  gear  E  is  in  dotted  position  the 
feed  rod  is  driven  by  belt  in  the  usual  manner.  When,  how- 


FIG.  246. 

ever,  change-gear  feeds  are  required  E  is  in  position  shown  and 
is  driven  by  the  gear  D  which  is  secured  on  the  sleeve  A  and 
receives  its  motion  through  the  change  gears  F  and  B.  The 
clutch  G,  which  slides  ove"r  a  key  in  the  lead  screw  L,  is  dis- 


THE  LATHE. 


173 


engaged  from  the  sleeve  A,  thus  preventing  the  lead  screw  from 
turning  while  the  feed  is  in  operation. 

As  the  carriage  must  be  capable  of  feed  in  either  direction,  a 
change  in  direction  of  motion  of  feed  mechanism  must  be  pro- 
vided for.  This  is  usually  accomplished  by  interposing  an  idle  gear 
either  in  the  mechanism  of  the  apron  and  allowing  the  feed  rod 
to  rotate  constantly  in  one  direction,  or  in  the  head-stock  gearing. 
The  latter  is  the  more  common  method,  inasmuch  as  a  change 
in  direction  of  lead  screw  rotation  is  necessary  and  that  cannot 
be  accomplished  in  the  apron.  In  Fig.  247  is  shown  the  arrange- 
ment of  gears  usually  employed.  Gear  A  is  secured  to  the  spindle 
of  the  lathe.  When  A  gears  with  B,  the  direction  of  rotation  of 
the  feed  cone  is  as  shown  by  the  arrow.  B  and  C  rotate  on  studs 
secured  in  a  plate  which  turns  about  the  axis  of  D.  By  throwing 
the  handle  H  down  and  C  into  mesh  with  A,  B  becomes  in- 


FIG.  247. 


FIG.  248. 


operative  and  the  direction  of  rotation  of  D  is  changed.  The 
stud  G  also  carries  one  of  the  change  gears  E.  The  diameter  of 
gears  B  and  C  is  immaterial,  inasmuch  as  they  are  simply  idlers 
between  A  and  D,  and  do  not  affect  the  velocity  ratio.  When 
gear  D  is  of  the  same  diameter  as  gear  A  the  stud  and  spindle 
have  the  same  rate  of  rotation.  D  is,  however,  frequently  made 
smaller  than  A,  giving  the  stud  a  higher  rate  of  rotation. 

The  mechanism  shown  in  Fig.  248  is  frequently  employed  for 
reversing  the  feed  in  lathes  and  other  machine  tools.  The  feed 
rod  C  carries  two  bevel  pinions  B  and  E  and  the  clutch  D.  D 
slides  over  a  key  in  C  and  engages  either  E  or  B,  both  of  which 
run  loose  upon  C  and  mesh  with  the  bevel  gear  A.  When  D  and 
E  are  locked  the  rotation  of  A  will  be  as  shown  by  arrow,  B 
turning  free  on  the  shaft,  and  when  B  and  D  engage  the  direction 
of  A  is  reversed. 


174 


MODERN    MACHINE   SHOP   TOOLS. 


The  lead  screw  is  one  of  the  most  important  parts  of  the  lathe, 
as  accurate  screw  threads  cannot  be  produced  with  an  inaccurate 
lead  screw.  The  builders  of  first  class  lathes  use  great  care  in 
the  production  of  their  screws,  the  lathe  used  for  cutting  them 
being  provided  with  -a  carefully  cut  master  screw  which  is  used 
only  for  the  cutting  of  lead  screws,  used  on  that  lathe.  The  wear 
on  this  master  screw  is  therefore  very  slight,  and  as  soon  as  the 
lead  screw  shows  signs  of  inaccuracy  the  master  screw  is  sub- 
stituted and  a  new  lead  screw  for  the  lathe  cut.  In  this  way  the 
standard  of  the  master  screw  is  very  closely  maintained. 

The  lead  screw  draws  the  carriage,  the  force  being  applied  at 
the  nut.  It  is,  therefore,  best  to  take  hold  of  the  carriage  as  close 
as  possible  to  the  shears  and  thus  avoid  the.  tendency  to  cramp 
the  carriage.  In  the  lathes  manufactured  by  the  American  Tool 


FIG.  249. 

Works  Company,  the  lead  screw  is  placed  inside  the  shears,  as 
shown  in  Fig.  240,  in  such  a  manner  as  to  get  the  most  direct  pull 
on  die  carriage. 

The  lead  screw  nut  is  made  in  halves  usually  of  brass  and  so 
mounted  in  the  apron  that  it  can  be  readily  closed  onto  the 
screw. 

In  order  to  cut  threads  of  different  pitches  with  the  same  lead 
screw  a  set  of  change  gears  must  be  provided  for  the  lathe,  so  that 
the  advance  of  the  screw,  carriage  and  tool  per  revolution  of  the 
spindle  may  be  exactly  equal  to  the  pitch  of  the  thread  being 
cut.  In  Fig.  249  is  shown  the  common  arrangement  of  change 
gear,  generally  called  a  single  gear.  Gears  A,  D,  and  E,  and 
the  stud  G,  correspond  to  the  same  parts  in  Fig.  247.  L  is  the 


THE  LATHE. 


175 


lead  screw,  B  the  gear  on  screw,  and  F  an  idler  of  any  con- 
venient size. 

In  cutting  any  number  of  threads  per  inch  the  point  of  the  tool 
must  move  along  the  work  an  amount  exactly  equal  to  the  pitch 
of  the  required  thread  for  each  revolution  of  the  work,  thus  if  the 
pitch  of  the  lead  screw  is  1-6  of  an  inch  and  the  pitch  of  thread  to 
be  cut  is  i-io,  it  is  evident  that  the  lead  screw  will  make  less  than 
one  revolution  while  the  work  is  making  one.  The  tool  has  ad- 
vanced i-io  of  an  inch  and  the  lead  screw  must  have  rotated 
through  6-10  of  one  revolution.  If,  therefore,  the  work  and  the 
screw  were  geared  together  the  ratio  6-10  would  represent  the 

..  teeth  in  gear  on  spindle      r~< .     ,. 

ratio  of r~- —  — .  This  direct  ratio  cannot  usually 

teeth  in  gear  on  screw 

be  used  as  the  gears  A  and  D  are  generally  of  different  diameters. 

Assume  A  as  having  40  teeth  and  D  20,  then  the  stud  G  makes 
two  revolutions  for  one  of  the  spindle  and  work.  Assume  the 
lead  screw  as  having  six  threads  per  inch,  to  determine  the  num- 
ber of  teeth  in  gears  E  and  B  to  cut  any  required  number  of 
threads  per  inch  on  the  work.  If  six  threads  are  required  the 
screw  must  make  one  revolution  to  the  work  one,  and  since  gear 
E  rotates  twice  as  fast  as  the  work  it  should  have  one-half  as 
many  teeth  as  gear  B. 

The  following  general  expressions  give  the  ratio  of  teeth  on 
stud  to  teeth  on  screw  in  problems  similar  to  the  above : 

Teeth  in  gear  on  stud        spindle  rotation        threads  on  screw 

. = X 

Teeth  in  gear  on  screw          stud  rotation          threads  on  \vork 

With  same  condition  as  above,  required  to  cut  i2l/2  threads : 
Teeth  in  stud  gear       i  6  6 

Teeth  in  screw  gear       2       12^/2       25 

As  6  is  too  low  a  number  of  teeth  for  practical  use  both  terms 
of  the  ratio  must  be  multiplied  by  some  number  that  will  give 
gears  of  reasonable  size.  In  the  present  case  use  3  which  gives  18 
teeth  in  stud  gear  and  75  in  screw  gear. 

Frequently  when  very  wide  ranges  of  screw  cutting  are  desired 
a  compound  system  of  gearing  similar  to  that  shown  in  Fig.  250 
is  used,  thus  avoiding  the  use  of  excessively  large  or  very  small 
gears.  In  this  arrangement  H  is  the  intermediate  stud,  I  the 


I76 


MODERN    MACHINE   SHOP    TOOLS. 


first  gear  on  stud  and  K  the  second.  This  gives  two  gear  reduc- 
tions in  place  of  one  in  the  single  gear  sKown  in  Fig.  249.  The 
calculations  for  determining  the  proper  number  of  teeth  in  each 
gear  to  cut  any  thread  with  the  compound  gearing  involves  one 
more  ratio  than  with  the  single. 

Assuming  the  velocity  ratio  of  the  stud  G  and  the  spindle  the 
same  as  in  Fig.  249,  and  the  lead  screw  %  pitch,  we  first  deter- 
mine the  velocity  ratio  between  the  stud  G  and  the  lead  screw 
necessary  in  cutting  the  required  number  of  threads  per  inch  on 
the  work.  For  example,  to  cut  100  threads  per  inch  we  would 
find  the  ratios  between  the  stud  and  screw  —  y2  X  8-100  =  1-25. 
As  we  would  not  care  to  use  a  gear  having  fewer  than  fourteen 


FIG.  250. 

teeth  on  the  stud,  a  gear  of  350  teeth  would  be  required  on  the 
screw  if  single  geared.  With  the  compound  gearing,  howrever, 
we  are  enabled  to  divide  this  ratio  into  factors  1-5  X  i~5  =  i-25- 
We  could  therefore  use  fifteen  teeth  on  gears  E  and  K,  and  75 
teeth  on  gears  I  and  B.  In  like  manner  if  70  threads  were  to  be 
cut  y2  X  8-70  —  8-140  =  4-70,  as  ratios  between  stud  and  screw 
—  2-10  X  2-7,  which  would  give  15  and  75  teeth  for  one  pair  and 
20  and  70  teeth  for  the  other  pair. 

Any  pair  of  gears,  in  which  the  teeth  have  the  required  ratio, 
may  be  used,  it  of  course  being  desirable  to  so  select  the  change 
gears  that  the  greatest  possible  number  of  required  pitches  may 
be  cut  with  as  small  an  assortment  of  change  gears  as  possible. 

In  order  to  avoid  the  time  lost  in  changing  gears  where  large 


THE  LATHE. 

varieties  of  different  pitch  threads  are  to  be  cut,  several  builders 
have  brought  out  lathes  in  which  the  change  gears  are  all 
mounted,  a  change  from  one  to  the  other  being  made  by  a  simple 
lever  movement.  In  Fig.  251  is  shown  this  class  of  change  gear 
mechanism  as  applied  to  the  Hendey-Norton  lathes.  It  will  be 
noticed  that  the  change  gears  are  all  mounted  on  the  lead  screw 
and  that  the  auxiliary  shaft  A  is  driven  through  the  gear  mechan- 
ism from  the  spindle  at  a  fixed  velocity  ratio  with  the  spindle. 
Gear  B  is  an  idler  mounted  on  the  shifting  lever  and  communi- 
cates the  motion  from  A  to  any  gear  on  the  lead  screw.  In  this 
manner  twelve  changes  in  pitch  may  be  obtained  without  chang- 
ing gears  and  for  each  change  in  size  of  gear  on  A  twelve  more 
pitches  may  be  cut. 

In  this  particular  lathe  the  reversing  mechanism  of  Fig  248  is 
applied  in  the  head  as  clearly  shown  in  cut.  By  a  suitable  com- 
bination of  levers  the  operating  of  the  reverse  is  controlled  by  a 
lever  in  the  apron  thus  allowing  the  work  to  run  in  one  direction 
all  the  time. 

In  a  mechanism  of  this  character  the  gears  must  be  rigidly 
mounted  and  accurately  cut  and  pitched,  as  otherwise  in  such 
long  trains  the  spring  and  back  lash  is  excessive. 

The  form  of  thread  usually  used  on  lead  screws  has  sides  of 
about  15  degree  angle,  as  this  form  allows  for  taking  up  the  wear 
in  the  nut  by  closing  it  onto  the  screw.  The  United  States  stand- 
ard thread  is  not  well  adapted  as  the  steep  angle  of  its  sides  forces 
the  nut,  which  is  necessarily  made  in  halves,  apart. 

The  lead  screw  and  nut  should  never  be  used  for  ordinary 
feeds  as  the  screw  would  soon  lose  its  accuracy,  through  wear. 
Unfortunately  for  the  accuracy  of  the  screw  a  comparatively  short 
portion  of  its  length  usually  does  most  of  the  leading  for  threads 
cut  in  the  lathe,  and  as  a  result  that  portion  becomes  worn  and 
inaccurate  while  the  balance  remains  in  good  condition. 

The  size  of  a  lathe  is  commonly  determined  by  its  swing  and 
the  length  of  the  bed,  the  swing  referring  to  the  greatest  diameter 
of  work,  when  held  on  the  face  plate  or  in  a  chuck,  that  the  lathe 
will  turn  over  the  shears.  Thus,  an  1 8-inch  by  10  foot  lathe 
means  one  that  has  a  bed  10  feet  long  and  will  swing  work  18 
inches  in  diameter.  The  builder  usually  allows  from  ^  to  ^  inch 
over  the  rated  swing,  thus  making  is  possible  to  actually  finish  a 
piece  of  work  of  the  same  diameter  as  the  normal  swing  of  the 
lathe.  The  swing  over  the  carriage  and  greatest  distance  between 


MODERN    MACHINE    SHOP    TOOLS. 


THE  LATHE. 


I79 


•centers  are  also  important  dimensions.  The  former  is  usually 
from  one-half  to  two-thirds  the  normal  swing  of  the  lathe. 

The  lathe  should  be  well  and  accurately  built,  of  ample  weight, 
with  operating  parts  conveniently  arranged.  Weight  is  desirable 
and  usually  indicates  a  first-class  tool.  This  is  not  necessarily 
true,  however,  as  frequently  a  badly  designed  machine  will  have 
certain  parts  excessively  heavy  with  other  parts  correspondingly 
light,  the  whole  often  making  an  unusually  heavy  machine — not 
so  good  as  the  lighter  machine  in  which  good  judgment  on  the 
part  of  the  designer  has  led  to  proper  proportions  for  all  the 
pafts. 

Lathe  builders  carefully  test  the  accuracy  of  their  lathes  be- 
fore sending  them  out.  As  it  is  frequently  desirable  for  the  me- 
chanic to  test  his  lathe  as  to  accuracy  of  alignment,  or  in  making 
repairs  on  lathes  that  have  become  inaccurate  through  wear,  the 
following  methods,  commonly  employed  for  this  purpose,  may  be 
of  value. 

To  determine  if  the  center  bearing  in  the  live  spindle  is  axially 
true  with  its  spindle:  Turn  up,  on  accurately  ground  centers, 
the  test  bar  shown  in  Fig.  252.  The  shank  S  should  fit  the  center 
bearing  nicely  and  the  collars  A  and  B  should  be  exactly  of  the 
same  diameter.  Place  the  test  bar  in  the  live  center  bearing, 
leaving  it  unsupported  at  the  outer  end,  and  cause  the  spindle  to 
rotate.  If  the  outer  end  of  the  bar  runs  perfectly  true,  then  the 
bearing  must  be  concentric  with  the  spindle.  By  using  the  test 
indicator  Fig.  105,  the  exact  amount  of  the  untruth,  if  any,  may  be 
determined. 

To  test  the  parallelism  of  the  live  spindle  and  the  shears :  If 
the  center  bearing  has  been  found  exactly  concentric,  place  the 
test  bar  in  the  bearing  as  before.  Put  a  fine  pointed  tool  or 
scriber  in  the  tool  post  and  so  adjust  that  it  will  just  touch  the 
top  of  the  collar  A.  Now  move  the  carriage  until  the  pointer  is 
over  the  collar  B.  If  it  touches  it  with  the  same  degree  of  contact 
as  on  A,  the  spindle  must  be  horizontally  parallel  with  the  shears 
and  line  of  motion  of  the  carriage.  In  like  manner  test  the  front 
side  of  the  collars  A  and  B  with  the  scriber,  and  if  as  before 
the  degree  of  contact  is  the  same  on  both,  the  spindle  must  be  ver- 
tically parallel  with  the  shears. 

To  test  the  carriage  cross  shears  at  right-angles  to  the  spindle : 
Take  a  very  light  cut  over  the  large  face  plate  and  test  with  a 
standard  straight  edge.  If  perfectly  plane,  the  alignment  is  cor- 


i8o 


MODERN    MACHINE    SHOP    TOOLS. 


rect.  If  the  face  plate  is  perfectly  true  and  it  is  not  -desirable  to 
take  a  cut  over  it,  a  smooth  ended  tool  held  in  the  tool  post  can 
be  brought  up  to  the  face  of  the  plate,  near  the  center,  just  close 
enough  to  pinch  a  piece  of  paper  lightly.  Now  move  the  rest 
out  to  the  outer  edge  of  the  plate  without  allowing  the  tool  or 
carriage  to  shift  along  the  bed,  and  if  the  paper  is  still  pinched 
to  the  same  degree  the  alignment  must  be  correct. 

Assuming  the  face  plate  as  true  both  on  its  face  and  circum- 
ference, to  test  the  alignment  of  the  tail  spindle :  Make  a  stub  A 
to  fit  the  tail  spindle  bearing  as  shown  in  Fig.  253.  Bring  the 


f 


A  (:  i 


FIG.' 253. 

spindle  back  until  the  tail  screw  starts  to  expel  the  stub  center 

A,  and  so  adjust  the  screw  that  when  A  bears  against  its  point 
a  smooth  turning  fit  between  A  and  the  spindle  bearing  results. 
C  is  an  arm  passing  through  A  and  secured  by  the  thumb  screw 

B.  D  is  a  pointer  which  passes  through  the  arm  C  and  is  held 
by  the  thumb  screw  I.     Adjust  the  point  E  so  it  touches  the 
upper  surface  of  the  circumference  of  the  face  plate  at  G.     Next 
swing  the  arm  around  until  point  E  comes  on  the  bottom  of  the 
plate  at  J.    If  E  touches  at  J  with  same  degree  of  pressure  as  at 
G,  then  the  tail  spindle  must  be  at  the  same  height  as  the  live 
spindle,  and  in  like  manner  if  it  bears  equally  on  the  two  sides, 
of  the  plate  the  cross  adjustment  must  be  right. 


THE  LATHE.  l8l 

In  order  to  determine  whether  the  center  line  of  the  tail 
spindle  is  coincident  with  that  of  the  live  spindle  we  can  reverse 
the  point  of  D  and  bring  F  into  contact  with  the  face  of  the 
plate  at  H.  If  it  maintains  uniform  pressure  of  contact  while  the 
arm  C  is  revolved  entirely  around,  then  the  dead  spindle  is  cen- 
tral and  parallel  with  the  live  spindle. 

If  the  tail  spindle  has  been  set  over  for  turning  taper  and  it 
is  desired  to  bring  it  back  central,  first  set  it  as  near  to  the 
correct  position  shown  by  the  lines  as  possible,  then  place  a  long 
bar  between  centers,  similar  to  the  one  shown  in  Fig.  252.  and 
take  a  very  light  cut  over  the  collars  A  and  B  without  changing 
the  transverse  position  of  the  tool.  Caliper  the  diameters  of  A 
and  B  accurately.  If  they  are  not  alike,  make  another  set-over 
adjustment  of  the  tail  stock  and  repeat,  continuing  to  do  so  until 
they  caliper  exactly  alike.  Two  trials  will  usually  be  found 
sufficient. 

To  test  the  truth  of  the  live  center,  place  a  bar  between  centers 
and  turn  a  small  portion  up  as  close  to  the  live  spindle  as  the 
dog  or  driver  will  permit ;  then  reverse  ends  with  the  bar  and  test 
the  turned  spot  for  truth  of  rotation.  If  perfectly  true  the  live 
center  is  running  true.  The  centers  in  the  test  bars  should  always 
be  carefully  reamed  and  lapped  or  worn  down  to  true  surfaces. 

It  is  difficult  to  keep  the  lathe  centers  in'  good  condition  and 
accurate  work  demands  that  they  be  so  kept.  The  dead  center 
must  be  true  and  hard  in  order  to  wear  well.  The  live  center 
need  not  be  so  hard,  inasmuch  as  there  is  no  wear  between  it  and 
the  bearing  in  the  work.  The  live  center  should  be  ground  in 
position  by  means  of  a  center  grinder.  After  being  ground  the 
live  center  should  be  removed  from  its  bearings  in  the  spindle  only 
when  absolutely  necessary,  as  it  is  practically  impossible  to  put 
it  back  and  have  it  perfectly  true.  A  small  prick  punch  mark- 
on  the  nose  of  the  spindle  and  a  corresponding  one  on  the  center 
will  enable  the  operator  to  put  the  center  back  as  nearly  as 
possible  in  its  correct  position.  It  is  advisable,  where  nice  work  is 
to  be  done,  to  always  grind  the  live  center  after  it  has  been  re- 
moved. The  center  should  always  be  ground  to  an  angle  of  ex- 
actly 60  degrees. 


CHAPTER  XIV. 

THE  LATHE  IX  MODIFIED  FORMS. 

In  Fig.  254  is  shown  the  Pratt  &  Whitney  lo-inch  tool-maker's 
lathe ;  a  tool  specially  designed  and  equipped  for  tool-room  work. 
The  greatest  refinements  in  lathe  manufacture  enter  into  the  con- 
struction of  this  tool.  The  equipment  that  usually  accompanies 
this  lathe  is  very  complete,  consisting  of  a  set  of  drawback  collets. 


FIG.  254. 

from  y%  to  y&  inch,  step  and  combination  chucks,  and  a  complete 
set  of  turning,  threading  and  knurling  tools. 

In  many  shops,  and  especially  those  doing  a  line  of  jobbing 
work,  it  frequently  becomes  necessary  to  turn  a  piece  of  work 
too  large  for  the  largest  lathe  in  the  shop.  The  time-honored 
practice  in  cases  of  this  kind  is  to  use  a  set  of  raising  blocks  under 


THE   LATHE   IX    MODIFIED   FORMS.  153 

head  and  tail  stocks  of  the  largest  swing  lathe  in  the  shop.  These 
blocks  are  planed  together  and  to  fit  the  shears,  thus  giving  the 
same  elevation  to  both  stocks  and  proper  alignment. 

The  McCabe  two-spindle  lathe,  is  a  tool  designed  to  meet 
these  conditions.  A  front  view  of  this  machine  is  shown  in  Fig. 
255  and  a  rear  view  in  Fig.  256.  The  general  construction  of  the 


FIG.  255. 


%  FIG.  256. 

tool  is  quite  clearly  shown  in  the  cuts.  The  lower  spindles  con- 
stitute a  standard  26-inch  engine  lathe  suitable  for  all  work  that 
would  ordinarily  be  performed  on  such  a  lathe.  By  placing  the 
pinion  shown  in  Fig.  255  on  the  nose  of  the  lower  spindle  and 
the  large  internal  geared  face  plate  on  the  upper  spindle  a  48-inch 
triple-geared  lathe  is  obtained.  The  elevating  tool  block  shown 
takes  the  place  of  the  compound  rest  when  using  the  upper  spindle. 


1 84 


MODERN    MACHINE   SHOP   TOOLS. 


A  very  wide  heavy  bed  is  used,  extending  well  out  under  both 
sets  of  spindles.  The  upper  spindles  set  back  of  the  lower  ones, 
which  with  a  short  extension  on  the  front  of  the  carriage  cross 
shear  allows  the  tool  to  be  set  sufficiently  back  from  the  center  to 
operate  correctly  upon  the  largest  work  the  upper  spindle  will 
swing. 

Still  another  form  of  lathe  intended  for  the  occasional  turning 
of  work  larger  than  the  normal  swing  will  permit  is  shown  in  Fig. 
257.  This  is  known  as  a  gap  lathe.  The  tool  shown  swings  16 
inches  with  gap  closed  and  32^  inches  with  gap  open.  The  con- 
struction is  quite  clearly  shown.  An  auxiliary  bed  carrying  the 
carriage  and  tail  stock  is  accurately  fitted  to  the  main  bed  and 


may,  by  means  of  a  rack  and  pinion  and  the  hand  wheel  shown,  be 
moved  away  from  the  face  plate  an  amount  sufficient  to  allow  the 
large-diameter  work  to  swing  through  the  gap. 

The  wheel  lathe  shown  in  Fig.  258  is  a  tool  specially  con- 
structed for  the  turning  of  locomotive  driving  wheels  in  place  on 
their  axle.  The  two  heads  are  geared  together.  The  work  is 
carried  on  centers  and  by  means  of  suitable  drivers  is  driven  from 
each  plate.  Both  wheels  are  operated  upon  at  the  same  time  by 
tools  held  in  separate  rests.  The  rests  are  compound  and  pro- 
vided with  automatic  feed,  actuated  from  overhead  rock  shaft 
and  ratchets  on  the  feed  screws. 

A  pit  lathe  is  one  used  for  the  turning  of  pulleys  and  balance 
wheels  of  large  diameter.  It  usually  consists  of  a  powerfully 


THE    LATHE    IX    MODIFIED    FORMS. 


18=; 


Beared  head,  an  outboard  bearing  or  support,  and  a  tool  rest.  The 
ted  is  built  up  of  masonry  with  a  pit  between  the  head  and  out- 
board bearing  in  which  the  wheel  operated  upon  may  swing.  The 
tool  rest  is  mounted  upon  a  cross  rail  which  is  supported  upon 


FIG.  258. 


plates  resting  on  the  pit  walls.    The  tool  is  provided  with  a  ratchet 
feed  automatically  operated. 

Pulley  lathes,  an  example  of  which  is  shown  in  Fig.  259,  are 
especially  designed  for  this  one  class  of  work.     They  are  usually 


FIG.  259. 


i86 


MODERN    MACHINE    SHOP    TOOLS. 


provided  with  two  tool  rests  and  a  revolving  tail  spindle  for 
boring  the  hub  at  the  same  time  the  rim  is  being  turned,  the 
pulley  being  held  in  a  chuck.  It  is  frequently  found  advisable, 
especially  on  smaller  pulleys,  to  bore  the  hub  in  a  chucking 
lathe  and  turn  it  in  the  pulley  lathe  on  a  mandrel  between  cen- 


ters. Special  carriers  attached  to  the  face  plate  should  be  used 
for  driving ;  the  drive  being  taken  on  the  arms  at  a  point  as  near 
the  rim  as  possible. 

When  a  number  of  similar  pieces,  requiring  several  opera- 
tions,  are   to  be   machined   in   an   engine   lathe,    much   time   is 


THE    LATIIK    IX     MODIKIKl)    FORMS. 


I87 


necessarily  lost  in  changing  from  one  cutting  tool  to  another. 
The  application  of  the  turret  head  to  a  standard  engine  lathe  as 
shown  in  Fig.  260  has  done  much  to  reduce  the  cost  of  produc- 
tion on  work  of  this  class.  The  turret  takes  the  place  of  the  tool 
block,  and  consequently  may  be  given  both  feeds  of  the  car- 
riage. 

When  equipped  with  drills,  reamers,  boring  and  facing  tools, 
it  may  be  used  to  good  advantage  on  a  wide  range  of  chucked 


m 


FIG.   201. 


FIG.   262. 

work.  When  equipped  with  box  turning  tools,  hollow  mills,  self- 
opening  dies  and  cut-off  slide,  it  becomes  well  adapted  to  rod 
work  on  steel  and  brass.  A  tapered  stop  pin  locates  the  turret 
central  with  the  spindle,  and  a  tempered  and  ground  index  ring- 
divides  exactly  the  rotation  about  the  vertical  axis. 

Other  forms  of  carriage  turrets  are  shown  in  Figs.  261  and 
262.  That  of  Fig.  262  is  arranged  to  carry  common  lathe  tools 
in  order  to  preserve  settings  on  duplicate  work. 


1 88 


MODERN    MACHINE    SHOP    TOOLS. 


In  Fig.  263  is  shown  an  engine  lathe  with  an  automatic  re- 
volving turret  on  the  shears  and  a  friction  back  gear.  The  turret 
is  provided  with  automatic  feed  actuated  by  an  independent  feed 
rod  at  the  back  of  the  bed.  The  turret  is  usually  operated  by  a 


FIG.  263. 

turnstile  as  shown,  the  mechanism  being  such  that  the  head  is 

rotated  through  one  division  by  the  last  portion  of  the  slide's 

stroke  in  carrying  it  back  from  the  work.  This  arrangement  of 


FIG.  264. 


THE    LATHE    IN    MODIFIED    FORMS. 


189 


turret  leaves  the  carriage  free  for  operations  upon  the  work 
simultaneously  with  the  tools  in  the  turret. 

In  Fig.  264  is  shown  a  plain  turret  machine.  The  turret  is 
hand  rotating  and  hand  feed.  The  usual  hand-operated  cross- 
slide  for  cut-off  and  forming  tools  is  provided.  This  constitutes 
the  turret  machine  in  what  is  termed  its  simplest  form. 

As  a  large  percentage  of  lathe  work  is  held  in  the  chuck  and 
requires  only  short  tool  travel,  classes  of  lathes  for  this  character 
of  work,  with  short  beds  fitted  with  turret  heads  and  known  as 
monitor  and  chucking  lathes,  are  made.  Fig.  265  illustrates  a 
monitor  lathe.  The  turret  slide  is  operated  with  a  lever  or 
screw  and  provided  with  a  cross  adjustment  for  facing.  >A 


FIG.  265. 

suitable  stop  on  the  cross  shear  enables  the  turret  to  be  readily 
brought  back  to  a  central  position.  These  lathes  are  made  either 
with  or  without  back  gears.  The  inclined  chaser  head,  which 
carries  an  inverted  tool  used  for  forming,  boring  and  threading* 
is  carried  on  a  rigid  chaser  bar  mounted  on  the  rear  of  the 
bed.  The  bar  slides  endwise  and  also  rotates  in  its  bearings, 
thus  allowing  the  head  to  be  turned  back  out  of  the  way  when 
not  in  use.  For  threading  purposes,  the  end  of  the  chaser 
bar  carries  what  is  known  as  the  "follower,"  which  engages  the 
threaded  "leader"  shown  at  the  left  of  the  head  stock.  The 
leader  may  be  of  any  desired  pitch  and  need  not  be  long,  as  the 
character  of  the  threads  cut  does  not  require  it.  As  many  of  the 
threads  cut  in  a  lathe  of  this  class  are  pipe  threads,  some  pro- 
vision must  be  made  for  cutting  them  on  a  taper.  In  the  ma- 


190 


MODERN    MACHINE    SHOP    TOOL'S. 


-chine  shown,  the  lever  rest  on  the  front  of  the  lathe  will,  when 
set  at  an  angle  with  the  top  of  the  shears,  throw  the  lever  and 
tool  out  as  it  advances  over  the  cut,  thus  producing  a  tapered 
thread.  By  raising  the  lever  at  the  end  of  the  cut,  the  follower  is 
<lis«ngaged,  and  the  tool  can  be  quickly  returned  for  another  cut, 


being  adjusted  to  its  cut  in  the  ordinary  manner.  These  lathes 
are  usually  furnished  with  a  simple  tool  rest  for  hand  turning. 
The  chaser  head  can  be  used  for  cutting-off  purposes.  A  cut-off 
tool  can  be  held  inverted  in  rear  tool  post  and  a  chamfering  or 
rounding  tool  held  in  the  other.  A  forward  motion  to  the  lever 
brings  the  cutting-off  tool  into  action.  After  the  work  is  cut  off 


I  III-:    LATHE    IN    MODIFIED    FORMS.  19! 

the  chamfering  tool  is  brought  into  action  by  an  outward  motion 
of  the  lever.  The  monitor  lathe  is  strictly  a  brass  finisher's  lathe 
and  very  largely  used  upon  all  classes  of  valves  and  fittings. 

In  Fig.  266  is  shown  a  plain  turret  screw  machine  with  wire 
feed.  This  is  a  plain  turret  lathe  intended  for  operating  upon 
rod  stock.  It  is  equipped  with  wire  feed  and  chuck,  which  are  so 
constructed  that  the  operator  may  feed  the  stock  forward  the 
required  amount  for  the  operation,  grip  it  in  the  chuck,  and  when 
finished  release  the  stock  in  the  chuck  without  stopping  the 
machine. 

Automatic  feed  is  often  applied  to  the  turret  slide  with  a 


FIG.  267. 

stop  to  knock  off  the  feed  at  any  desired  point.  The  larger  ma- 
chines are  usually  back  geared ;  the  friction-geared  head,  which 
permits  throwing  in  the  back  gear  without  stopping,  being  the 
form  quite  generally  used.  An  automatic  oil  pump  supplies  a 
flood  of  oil  for  lubricating  the  cutting  tools  and  carrying  away 
the  heat. 

The  automatic  screw  machine,  an  example  of  which  is  shown 
in  Fig.  267,  is  a  machine  designed  for  the  automatic  production 
of  machine  screws  and  a  large  variety  of  small  work  that  can 
be  cut  from  the  end  of  bar  stock.  All  movements  are  entirely 


1 92 


MODERN    MACHINE    SHOP    TOOLS. 


automatic  and  controlled  by  quick-moving  cams.  All  dead  move- 
ments, as  the  setting-  up  of  the  stock,  the  return  of  the  turret  slide 
and  the  rotation  of  the  turret,  are  made  very  quickly  by  shafts 


running  at  constant  speeds  and  irrespective  of  the  speeds  used  for 
the  work  movements. 

In  Fig.  268  is  shown  a  view  of  the  Gisholt  turret  chucking 


THE    LATHE    IN    MODIFIED    FORMS.  193 

lathe.  This  is  a  massive  tool  powerfully  geared  and  capable  of 
producing  large  quantities  of  duplicate  work.  A  heavy  cross 
carriage  and  inclined  turret  are  mounted  on  the  shears.  External 
operations  are  largely  performed  by  broad-faced  tools,  held  in 
the  cross  carriage  and  the  boring  and  other  internal  operations 
by  tools  mounted  in  the  turret.  Bushings  in  the  nose  of  the 
spindle  are  used  for  steadying  the  boring  bars.  All  the  formed 
cutters  are  provided  with  hardened  and  ground  extension  or 
pilots,  which  fit  bushings  in  the  chuck,  spindle,  or  work,  thus 
steadying  the  tool  and  adding  much  to  its  efficiency.  These  lathes 
are  regularly  equipped  with  taper  attachments  and  screw-cutting 
gear. 

The   double-turret   manufacturers'   lathe   shown   in   Fig.   269 


FIG.  269. 

is  also  a  tool  for  operating  upon  chucked  work  that  is  to  be  pro- 
duced in  duplicate.  In  this  tool  two  turrets,  one  a  boring  and 
facing  turret,  the  other  a  turning  turret,  are  mounted  upon  a 
revolving  plate  in  such  a  manner  that  either  may  be  brought  into 
operation  as  desired.  The  machine  is  equipped  with  a  lever 
operated  scroll  chuck,  which  permits  of  putting  in  and  removing 
work  without  stopping  the  spindle. 

In  Fig.  270  is  illustrated  an  automatic  chucking  machine. 
This  machine  is  designed  to  perform  automatically  the  several 
operations  required  in  the  finishing  of  a  great  variety  of  chucked 
work.  The  time  of  the  operator  is  required  only  for  chucking 
and  truing  each  piece  operated  upon.  It  is  therefore  possible 
for  one  man  to  operate  several  machines.  As  with  the  automatic 
screw  machine,  all  dead  movements  are  made  at  very  quick 
speeds. 


194 


MODERN    MACHINE    SHOP    TOOLS. 


In  Fig.  271  is  shown  the  "flat-turret"  lathe,  a  tool  specially 
adapted  to  the  rapid  production  cf  a  great  variety  of  work  cut 
from  bar  stock.  The  capacity  of  the  machine  is  2  inches  in 


/ 


FIG.   270. 


FIG.   271. 


diameter  by  24  inches  long,  the  arrangement  of  the  tools  on  the 
flat  turret  being  such  as  to  allow  the  work  to  pass  through  a 
distance  not  exceeding  24  inches. 


THE    LATIIK    IX    MODIFIED    FORMS. 


195 


In  Fig.  272  is  shown  a  top  view  of  the  turret,  showing  the 
tools  in  place.  The  bearing  of  the  turret,  which  is  gibbed  at 
its  outer  edge,  is  large.  The  tools  do  not  overhang  and  are 
consequently  very  rigid.  The  automatic  chuck  used  on  this 


FIG.  272. 

machine  is  shown  in  section  in  Fig.  273.  It  is  shown  in  the 
closed  position.  By  moving  the  outside  collar  to  the  right  the 
jaws  are  released,  and  the  work  by  means  of  an  ingenious  roller 
feed  is  advanced  for  the  next  operation.  The  chuck  jaws  may 
be  removed  and  replaced  by  others  of  any 
desired  size  or  form  within  the  capacity 
of  the  chuck. 

The  ''hollow  hexagon  turret'7  lathe  is 
shown  in  Fig.  274.  In  this  lathe  the 
tools  are  secured  to  the  sides  of  a  hollow 
hexagon,  thus  allowing  the  work  to  pass 
through.  The  maximum  capacity  of  the 
machine  is  2  inches  diameter  by  24  inches 
in  length.  The  bed  rests  upon  a  three- 
point  support  to  prevent  twisting  when 

standing  on  an  uneven  foundation.  Many  valuable  features 
characteristic  of  the  other  tools  by  its  builders  enter  into  the 
construction  of  this  lathe. 

The    pipe-threading    machine    and    cutting-off    machine    are 


FIG.  273. 


196  MODERN    MACHINE    SHOP    TOOLS. 

special  forms  of  turning  lathes  designed  for  their  particular  class 
of  work.  The  accelerated  speed  cutting-off  machines  are  oper- 
ated by  a  variable  drive  so  arranged  that  as  the  cutting-off  blades 
approach  the  center  of  the  bar  the  speed  of  rotation  increases  and 
thus  maintains  a  nearly  constant  cutting  speed  from  outside  to 
center  of  the  work. 

Lathe  countershafts,  and  in  fact  all  machine  tool  counter- 
shafts, are  important  adjuncts  to  the  machine  which  unfortu- 
nately do  not  always  receive  the  proper  amount  of  thought  on  the 
part  of  the  designer  or  care  in  their  construction.  Many  ex- 
cellent tools  are  sent  out  with  inferior  countershafts,  and  as  they 


FIG.  274. 

are  quite  apt  to  be  neglected  by  the  user,  especially  in  breaking  in., 
they  very  soon  give  trouble.  The  boxes  should  be  self-oiling- 
and  the  loose  pulleys  provided  with  means  for  proper  lubrication. 
When  tight  and  loose  pulleys  are  used,  it  is  desirable  to  have  the 
loose  pulley  somewhat  smaller  in  diameter  than  the  tight,  thus 
relieving  some  of  the  belt  tension  when  on  the  loose  pulley.  A 
smooth,  reamed  pulley  bore  and  a  smooth-finished  and  carefully 
fitted  shaft  will,  when  properly  oiled,  give  desired  results. 
Clutch  pulleys  especially  for  reversing  countershafts  are  much 
used.  They  should  be  simple  and  admit  of  proper  lubrication* 
and  adjustment. 


CHAPTER  XV. 

LATHE    TOOLS. 

On  the  subject  of  cutting  tools  for  the  lathe  we  will  consider 
only  the  more  general  points,  as  practice  alone  can  bring  out 
the  details  of  proper  form  and  setting. 

The  common  lathe  tool  as  shown  in  Fig.  275  is  a  short  bar  of 
tool  steel  of  rectangular  cross  section  having  a  cutting  edge 
formed  on  one  end  by  forging  and  grinding.  The  cutting  edges 


FIG.  275. 

must  be  hardened  and  tempered  in  order  that  they  may  properly 
cut  the  metals  upon  which  they  operate.  The  form  of  the  cutting 
edge  depends  upon  the  kind  and  hardness  of  the  metal  to  be 
cut,  the  amount  of  metal  to  be  removed  and  whether  the  cut  is 
to  be  a  roughing  or  a  finishing  one.  These  tools  when  new  are 
made  from  six  to  twelve  inches  long,  their  length  depending 


FIG.  276. 


FIG.  277. 


upon  the  size  of  the  lathe  in  which  they  are  to  be  used.  As  the 
edges  wear  and  are  ground  away  they  are  redressed,  thus, 
gradually  using  up  the  stock  and  finally  leaving  a  short  stub, 
that  is,  as  a  lathe  tool,  of  no  further  value. 

The  cutting  edge  of  the  lathe  tool,  as  shown  in  Fig.  276,  has 


198 


MODERN    MACHINE    SHOP    TOOLS. 


what  we  term  an  angle  of  clearance  A  and  an  angle  of  rake  B. 
The  angle  of  clearance  has  the  greatest  strength  value,  as  the 
smaller  this  angle  the  greater  the  support  given  the  cutting  edge. 
¥or  facing,  the  tool  must  have  some  clearance  as  otherwise  the 
cutting  edge  is  held  away  from  the  work.  On  cylindrical  work 
if  set  somewhat  below  the  center,  it  will  clear  the  body  of  the 
work  but  will  not  properly  clear  the  feed. 

The  greater  the  angles  of  rake  and  clearance  the  more  acute 
will  be  the  cutting  edge  and  the  finer  and  smoother  the  cut.  If 
the  edge  is  too  acute,  however,  it  will' not  stand  up  to  the  work 
properly.  The  angle  of  rake  has  the  greatest  cutting  value,  as 
strength  of  cutting  edge  prevents  excessive  clearance. 

A  tool  may  have  front  rake  as  in  Fig.  278,  or  side  rake  as  in 
Fig.  277.  It  is  usual,  however,  to  grind  it  with  both  front  and 
side  rake  as  shown  in  Fig.  278.  A  tool  without  rake  requires 


FIG.  278. 


FIG.  279. 


greater  force  to  drive  it  through  the  cut  as  it  tears  rather  than 
cuts  the  metal.  It  does  not  leave  a  smooth  surface  and  springs 
the  work  unduly. 

For  general  practice  the  angle  of  clearance  should  be  small, 
only  enough  to  properly  clear  the  cutting  edge,  from  5  to  15, 
degrees  usually  being  sufficient.  The  angle  of  rake,  on  the  other 
hand,  should  be  as  great  as  the  character  of  the  tool  and  hard- 
ness of  the  work  will  permit.  The  small  clearance  angle  gives 
good  support  to  the  cutting  edge  and  prevents  its  dipping  into 
the  work.  The  large  angle  of  rake  gives  keenness  to  the  cutting 
edge,  making  a  tool  that  cuts  smoothly  and  free.  For  these 
acute  cutting  edges  the  temper  cannot  be  too  hard,  as  in  that 
case  the  edge  chips  off.  As  the  hardness  of  the  metal  operated 
upon  increases,  the  angle  of  rake  must  be  reduced  and  the  hard- 
ness of  the  cutting  edge  increased. 


LATHE    TOOLS. 


199 


The  above  does  not  apply  to  the  working  of  brass,  as  that 
metal  should  be  worked  with  a  tool  having  slight  clearance 
and  no  rake. 

For  the  same  rate  of  feed  a  tool  operating  upon  work  of 
small  diameter  must  have  a  greater  angle  of  clearance  than  is 
necessary  when  used  on  work  of  large  diameter,  as  the  same 
feed  gives  a  greater  pitch  angle  in  the  former  case.  This  is 
clearly  shown  in  Fig.  279. 

It  is  always  desirable  when  a  heavy  cut  is  being  taken  to 
have  that  part  of  the  cutting  edge  presented  to  the  work  as 
short  as  the  strength  and  durability  of  the  edge  will  permit. 
A  straight  cutting  edge,  A.  Fig.  280,  at  right  angles  to  the  axis 
of  the  work  presents  the  shortest  possible  length  of  cut,  but  the 
delicate  point  of  such  a  tool  will  not  stand  up  well.  If  rounded 
somewhat  as  shown  at  B,  we  get  a  cutting  length  but  slightly 


L 

x_                                                                       „ 

—     c                   /^~~ 

J   i 

B 

j            ^ 

C 

i  ' 

A 
FIG.  280.                                                FIG.  28l. 

greater  and  of  a  durable  form.  If  the  point  is  too  broad,  as 
shown  at  C,  undue  resistance  is  offered  owing  to  the  long  line  of 
cutting  action. 

That  portion  of  the  cutting  edge  which  lies  parallel  to  the 
axis  of  the  work  produces  the  finish  while  the  portion  at  right 
angles  to  the  axis  removes  the  metal.  The  finishing  portion  of 
the  cutting  edge  should  be  considerably  longer  than  the  rate  of 
feed,  thus  producing  a  smooth  finished  surface.  If  the  cut  is 
light  and  the  edge  parallel  to  the  axis  is  long,  the  tendency  for 
the  tool  to  dip  or  dig  into  the  work  is  great  and  especially  so 
when  the  angle  of  clearance  is  excessive  and  the  cutting  edge 
set  high  above  the  center. 

In  general  a  tool^works  best  when  set  for  height  at  or  slightly 
above  the  center.  When  above  the  center  any  spring  in  the 
tool  or  work  causes  the  tool  to  clip  into  the  work  and  leave  an 
untrue  surface.  Soft  spots  in  the  metal  or  irregular  depth  of 


2OO  MODERN    MACHINE    SHOP    TOOLS. 

cut  will  increase  this  trouble.  As  the  spring  comes  from  the 
tool  post  block  and  points  below  the  cutting  edge,  setting  the 
tool  down  to  the  center  of  the  work  reduces  but  does  not  over- 
come this  difficulty.  If  the  tool  rest  was  perfectly  rigid  then  a 
tool  having  its  cutting  edge  dropped  to  a  line  even  with  the 
bottom  of  the  tool  at  point  of  support  would,  owing  to  its  own 
deflection,  swing  out  rather  than  into  the  work  when  set  at  or 
below  the  center.  In  all  cases  the  tool  should  be  held  as  firmly 
as  possible  and  well  back  in  the  tool  post. 

In  setting  a  tool  for  a  heavy  cut  it  should  when  possible  be 
set  raking  back  rather  than  ahead  as  in  case  of  its  slipping  in 
the  tool  post  it  will  swing  out  of  the  work  rather  than  into  it. 
This,  of  course,  cannot  be  done  when  it  is  necessary  to  take  the 
cut  close  up  to  the  dog  or  driver. 

Cutting-off  tools  work  free  and  smooth  when  given  a  small 
amount  of  top  rake.  As  with  other  tools,  however,  when  used 
on  brass  they  should  have  no  top  rake  and  will  frequently  be 
found  to  work  better  with  a  small  amount  of  negative  rake. 

The  boring  tool  as  commonly  forged  from  bar  steel  is  shown 
in  Fig.  281.  The  diameter  and  length  of  the  stem  depend  upon 
the  size  and  depth  of  the  bore  in  which  the  tool  is  to  be  used. 
This  tool  is  necessarily  a  springy  one  and  should,  therefore,  be 
as  short  and  heavy  as  possible,  thus  requiring  a  large  assort- 
ment of  sizes  for  any  range  of  work. 

Tungsten  or  self-hardening  steel  has  come  into  quite  general 
use  for  lathe  tools.  It  is  an  "air  hardening"  steel,  and  after 
forging  must  be  kept  from  water.  As  it  is  "hot  short"  it  is  ex- 
ceedingly difficult  to  forge  into  any  other  than  the  most  simple 
forms.  Its  great  value  over  ordinary  tool  steel  lies  in  its  hard- 
ness and  temper-holding  quality,  which  makes  it  possible  to  use 
higher  cutting  speed  without  injury  to  the  cutting  edge  due  to  the 
heating.  It  is  several  times  more  expensive  than  the  best  grades 
of  ordinary  tool  steel,  and  for  this  reason  and  also  on  account 
of  the  difficulties  met  with  in  forging  it,  numerous  forms  of 
holders  for  its  efficient  and  economical  use  have  been  introduced. 
In  all  such  tools  only  the  cutting  portion  is  of  the  self-harden- 
ing steel,  the  holder  being  a  drop  forging  of  mild  steel.  The 
cutting  portion  is  of  such  form  that  it  can  be  kept  in  proper 
condition  for  work  by  simply  grinding  it,  thus  avoiding  the  ex- 
pense of  forging.  In  Fig.  282  is  shown  an  Armstrong  tool 
holder  of  this  class  with  straight  body.  It  is  also  made  right 


LATHE    TOOLS. 


2O I 


and  left,  a  left-hand  holder  being  one  with  the  cutting  point 
offset  so  as  to  make  an  angle  to  the  right  and  a  right-hand 
holder  having  the  cutter  pointing  to  the  left.  A  right-hand 
"holder  is  shown  in  Fig.  283. 

As  several  cutting  points  may  be  used  in  one  holder,  a  tool 


FIG.  282. 

of  this  character  frequently  takes  the  place  of  a  number  of 
forged  tools.  They  possess  many  points  of  superiority  over 
the  common  forged  lathe  tool  and  are  being  extensively  used  in 
many  of  the  best  shops.  For  very  heavy  high-speed  turning  they 
are  not  as  good  as  a  heavy  tool  forged  from  self-hardening  steel, 


FIG.  283. 

due  to  the  fact  that  the  small  quantity  of  steel  used  will  riot 
conduct  away  the  heat  as  will  the  larger  body  in  the  forged  tool. 
For  this  reason  it  is  always  advisable  to  use  as  large  a  holder 
for  any  job  as  its  nature  and  the  size  of  the  lathe  will  permit. 

An    inserted    blade    cutting-off    tool    by   the    same    maker    is 
shown  in  Fig.  284.     In  tools  of  this  class  the  blade  is  securely 


FIG.  284. 

clamped  in  the  holder  and  may  be  extended  an  amount  just  suffi- 
cient to  make  the  required  depth  of  cut,  thus  insuring  the  maxi- 
mum strength  of  blade  in  every  case.  The  blades  are  carefully 
ground  to  thickness,  given  the  necessary  clearance  and  sharpened 
fry  grinding  from  the  end  and  top. 


202 


MODERN    MACHINE    SHOP    TOOLS. 


The  Hill  bent  cutting-off  tool  shown  in  Fig.  285  is  a  simple 
and  reliable  tool.  The  blade  is  firmly  held  in  the  holder  by  the 
clamp  bolts  shown.  The  blades  are  of  self-hardening  steel. 


FIG.  285. 

A  modification  of  this  tool  as  shown  in  Figs.  286  and  287 
has  made  a  unique  and  substantial  side-cutting  tool.  These  tools 
are  made  right  and  left  hand. 

They  have  self-hardening  blades  and  should  be  ground  mostly 


FIG.  286. 


from  the  end,  the  side  and  top  grinding  giving  the  clearance  and 
fake.  They  are  a  very  satisfactory  substitute  for  the  forged  side 
tool  on  all  classes  of  work. 

The  Mingst  ring-cutting  tool,  Fig.   288,   is  a  box  holder   in 


FIG.  287. 


FIG.  289. 


which  two  cutting-off  blades  may  be  held.     By  using  distance 
blocks  between  them,  rings  of  any  width  within  the  capacity  of 


LATHE    TOOLS. 


203 


the  tool  may  be  cut  to  uniform  width.  The  first  cutter  is  usually 
set  slightly  in  advance  of  the  second  and  serves  more  as  a  guide 
than  a  cutting  tool.  It  is  frequently  desirable  to  convert  the 
first  blade  into  a  side-cutting  tool  and  let  it  give  a  truing  cut 
over  the  edge  of  the  ring  and  ahead  of  the  cutting-off  blade. 

The  tool  shown  in  Fig.  289  is  one  of  the  several  patent  tools 
which  meet  the   requirements   of   a   first-class   boring  tool   very 


FIG.  290. 

nicely.  The  stem  which  carries  a  small  cutting  point  of  self- 
hardening  steel  can  be  extended  for  any  required  /depth  of  bore 
within  the  limits  of  the  tool.  It  is  provided  with  two  cutter- 
holding  tips  as  shown.  At  A  and  B,  Fig.  290,  are  illustrated 
examples  of  work  this  tool  is  adapted  to. 

A  simple  tool  of  this  class  is  shown  in  Fig.  291.     The  bent 


FIG.  291. 


shank  is  frequently  a  point  of  convenience,  especially  when  it  is 
necessary  to  use  a  small  size  of  holder  in  a  large  tool  post. 

The  same  rules  for  angles  of  rake  and  clearance  apply  to  the 
boring  tool  as  for  tools  on  external  work. 

A  threading  tool,  although  a  simple  tool  to  forge,  is  a  difficult 
one  to  grind  and  get  correct  in  angle,  clearance  and  lead.  The 
patent  threading  tools  that  can  be  ground  without  changing 
their  form  have  as  a  result  come  into  very  general  use.  The 
tool  shown  in  Fig.  292  has  a  bent  holder  with  a  cutter,  capable 


204 


MODERN    MACHINE    SHOP    TOOLS. 


of  rotation,  attached  to  it.  The  cutter  is  correctly  ground  in  its 
angle  and  is  sharpened  by  radial  grinding  on  the  top  of  the 
cutting  surface.  The  upper  portion  of  the  cutter  is  serrated, 
allowing  the  set  screw  together  with  the  clamp  bolt  to  hold  it 
firmly  in  position.  The  form  is  such  that  the  angular  surfaces 
-approach  the  center  as  the  cutting  face  is  ground  back,  thus  main- 


FIG.  292. 

taining  proper  clearance.  The  plane  of  the  cutter  is  slightly  in- 
clined from  that  of  the  holder,  to  accommodate  the  tool  to  the 
average  lead  of  the  pitches  cut. 

The  Pratt  &  Whitney  threading  tool,  Fig.  293,  has  a  straight 
cutter  correctly  ground  in  the  angle  and  firmly  clamped  in  the 
holder.  One  corner  of  the  cutter  is  provided  with  threads  which 
engage  the  threads  on  the  small  locking  screw  shown.  This 


FIG.  293. 

cutter  is  ground  from  the  top  face.  The  offset  cutter  shown  in 
the  figure  is  used  for  cutting  close  up  to  a  shoulder.  This  holder 
is  also  used  for  holding  chasers  and  formed  cutters  of  various 
outlines. 

The  Rhodes  square-threading  tool,  Fig.  294,  is  a  form  of  tool 
holder  for  the  cutting  of  square  threads.     Blades   for   any   de- 


LATHE    TOOLS. 


205 


sired  pitch  of  thread  to  be  cut  are  clamped  as  shown.  The  form, 
of  the  blade  and  the  angle  of  the  groove  in  the  holder  give  the 
proper  clearance  and  average  lead  for  cutting  right-hand  threads 


FIG.  294. 


FIG.  2or. 


MOPERN    MACHINE    SHOP    TOOLS. 


when  clamped  as  shown,  and  for  left-hand  threads  when  clamped 
in  the  other  end  of  the  holder. 

The  Rivett-Dock  thread-cutting  tool  shown  in  Fig.  295  is  a 
tool  which  cuts  a  thread  in  an  entirely  different  manner  from  the 
regular  formed  tools.  It  consists  of  a  round  cutter,  resembling 
somewhat  a  gear  cutter,  mounted  upon  a  slide  and  controlled  by 
a  lever.  There  are  ten  teeth  in  the  cutter,  all  correctly  formed 
in  the  angle,  but  each  tooth  is  of  a  height 
to  cut  deeper  than  the  preceding  one.  In 
Fig.  296  is  shown  by  the  dotted  lines  the 
successive  cuts  made  by  the  teeth  from  I 
to  10.  The  cutter  is  drawn  back  from 
the  work  and  the  next  tooth  turned  into 
position  for  its  cut  by  means  of  the  hand 
lever.  The  bottom  of  the  cutting  tooth 
rests  upon  a  substantial  support. 

It  will  be  noted  that  the  teeth  remove  the  stock  almost  en- 
tirely by  an  end  cut,  the  full  width  of  the  thread  being  finished 
by  each  tooth.  The  effect  of  this  method  is  to  prevent  tearing 
up  the  sides  of  the  thread,  as  so  often  happens  with  the  common 
threading  tool,  where  the  cut  is  entirely  on  the  sides. 

The  knurling  tool,   Fig.   297,   is   a   lathe   tool   in   which   two 


PIG.  296. 


FIG.  297. 

knurling  mills  are  mounted  upon  pivots  in  a  head  pivoted  in  the 
holder,  the  object  of  the  latter  adjustment  being  to  allow  the 
mills  to  bear  with  equal  pressure  against  the  work. 

Tools  for  lathes  of  the  turret  class  are  largely  made  up  of 
standard  small  tools,  as  drills,  boring  bars,  taps  and  reamers  for 


LATHE    TOOLS. 


207 


the  inside  work  with  special  forming  and  box  tools  for  the  ex- 
terior surface  work. 

In  Fig.  298  is  shown  a  forming  block  and  formed  cutter. 
This  tool  is  securely  bolted  to  the  carriage  block  or  cut-off  rest. 
The  cutter  is  firmly  attached  to  the  block  and  is  of  such  a  form 


FIG.  298. 

as  to  produce  the  required  irregular  outlines.  The  top  of  the 
cutter  should  be  at  the  height  of  the  lathe  spindle.  A  swinging 
cut-off  tool  is  usually  attached,  as  shown,  for  cutting  off  the  stock- 
after  it  is  formed  up. 

A  box  milling  tool  or  turner  is  shown,  front  and  back  view, 
in  Fig.  299.     These  tools  are  secured  to  the  turret.     They  consist 


FIG.  299. 


208 


MODERN    MACHINE    SHOP    TOOLS. 


of  a  hardened  adjustable  back  rest  and  holder  in  which  the 
cutting  tool  is  secured.  The  tool  and  holder  may  be  adjusted 
for  obtaining  proper  depth  of  cut.  The  holder  in  this  tool  mayr 
by  means  of  a  cam  and  lever,  be  thrown  back  when  the  tool  is 
removed  from  the  work,  thus  preventing  the  cutter  from  scratch- 
ing the  finished  surface. 

A  pointing  box  tool  is  shown  in  Fig.  300.  It  is  designed  for 
pointing  up  or  crowning  the  end  of  bar  work. 

In  Fig.  300  A  is  shown  an  adjustable  lathe  or  box  mill.     This 


FIG.  300. 


FIG.  300  A. 


tool  is  carried  in  the  turret  and  works  over  the  end  of  bar  stock. 
The  cutters  are  mounted  in  such  a  manner  that  they  may  be  ad- 
justed to  turn  any  diameter  within  the  range  of  the  tool.  The 
cutters  cut  from  the  end,  the  inner  portion  serving  to  guide  and 
steady  the  work.  In  setting  to  a  required  diameter  the  cutters 
may  be  set  down  onto  a  standard  hardened  plug  gauge  of  that 
diameter. 


FIG.  301. 


LATHE    TOOLS.  200, 

The  box  cut-off  slide  as  used  on  the  turret  is  illustrated  in 
Fig.  301.  It  consists'  of  a  substantial  back  in  which  the  tool- 
carrying  frame  is  gibbed.  A  pinion  pivoted  in  the  back  engages 
a  rack  on  the  frame,  and  by  means  of  the  lever  on  the  pinion  shaft 
a  steady  movement  of  the  cut-off  tool  may  be  had.  Suitable 
stops  make  it  possible- to  cut  to  an  exact  depth  on  any  number  of 
pieces. 

A  mechanic's  success  as  a  lathe  hand  depends  very  largely 
upon  the  skill  and  judgment  he  exercises  in  the  grinding  and 
setting  of  the  cutting  tools.  They  must  at  all  times  be  kept  in 
proper  condition.  A  dull  or  improperly  formed  tool  will  not 
do  satisfactory  work  and  is  frequently  the  cause  of  serious  injury 
or  accident  to  the  work. 


CHAPTER  XVI. 

CHUCKS  AND  DRIVERS   FOR  LATHE  WORK. 

The  dog  or  driver  connects  the  work  with  the  spindle  of  the 
lathe,  and  in  its  common  form  is  shown  in  Fig.  302.  For  all 
ordinary  work  this  device  serves  its  purpose  well ;  for  very  ac- 
curate work,  however,  the  effect  of  its  leverage  must  be  taken 
into  consideration.  As  shown  at  A  in  the  figure,  the  distance  be- 
tween the  dotted  lines  represents  the  lever-arm,  which  acts  on  the 
center  as  a  fulcrum,  and  produces,  or  tends  to  produce,  a  deflec- 
tion in  the  work.  Again,  the  force  being  applied  at  D,  and  the 


FIG.  302. 

pressure  of  the  cut  at  C,  the  tendency  to  bend  the  work  will  be 
greater  than  when  the  point  D  has  moved  round  180  degrees,  or 
on  the  same  side  as  the  tool.  The  first  of  these  objections  is 
overcome  by  using  the  straight-tail  dog,  as  shown  in  Fig.  303, 
with  a  stud  or  driver  bolted  on  the  face  plate,  and  the  second,  by 
using  a  double-ended  dog  and  driving  from  opposite  sides,  as 
shown  in  Fig.  304.  The  use  of  the  double-ended  dog  is  usually 
not  altogether  satisfactory,  as  it  is  very  difficult  to  so  adjust  the 
drivers  that  the  pressure  aganst  each  will  be  uniform.  Double- 
ended  dogs  are  frequently  made  adjustable.  The  usual  way, 
however,  is  to  adjust  the  driver  pins  rather  than  the  dog. 

As  the  dogs  above  shown  depend  on  a  screw  to  hold  them  se- 
curely on  the  work,  care  must  be  exercised  or  the  work  is  very 


CHl'C 


AXI)    DRIVERS    FOR    LATHE    WORK. 


211 


•apt  to  be  injured.  The  screw  should  always  have  a  hardened 
flat  or  oval  point.  While  such  a  point  does  not  hold  as  rirmiy 
as  the  cupped  point,  it  does  not  cut  into  the  work  as  badly.  When 
used  on  finished  work  a  ferrule  of  sheet  brass,  or  preferably, 
copper  should  be  put  on  the  work  under  the  dog  to  prevent  any 


FIG.  303. 


FIG.   304. 


injury  to  the  work  surface.  The  screw  should  be  tightened 
enough  to  safely  drive  without  slipping.  If  the  dog  slips  it  is 
quite  certain  to  injure  the  surface. 

For  many  cases,  and  more  especially  on  finished  work,  the  die 


FIG.  305. 

and  clamp  dogs,  shown  at  A  and  B  respectively,  Fig.  305,  are  ex- 
cellent. These  dogs  are  very  nicely  made  of  forged  steel  and 
hardened. 


212 


MODERN    MACHINE    SHOP    TOOLS. 


In  Fig.  306  is  shown  a  form  of  clamp  dog  very  well  adapted 
to  the  holding  of  tapered  work. 

In  Fig.  307  is  shown  a  bolt  dog.  This  tool  is  clamped  to  the 
face-plate  so  as  to  receive  the  head  of  the  bolt.  It  will  drive 


FIG.  306. 

square  or  hexagon  head  bolts,  and,  where  a  number  are  to  be 
operated  upon,  will  save  the  time  that  would  be  required  to  put 
on  and  take  off  the  common  dog. 

When  a  dog  must  be  used  on  the  threaded  end  of  a  bolt  or 


FIG.  307. 

spindle  it  is  necessary  to  protect  the  thread,  or  it  will  be  injured 
by  the  dog  screw.  If  the  work  to  be  driven  does  not  require  the 
screw  to  be  tightened  very  hard,  a.  heavy  piece  of  brass  over  the 
thread  will  usually  be  found  satisfactory.  A  common  practice 


CHUCKS    AND    DRIVERS    FOR    LATHE    WORK. 


2I3 


in  cases  of  this  kind  is  to  jamb  two  nuts  on  the  thread  and  place 
the  dog  on  the  outer  nut.  In  Fig.  308  is  shown  a  very  satisfac- 
tory form  of  dog  for  use  in  such  cases.  It  should  be  made  of 
forged  steel,  tapped  the  required  thread,  and  split  as  shown. 
The  clamp  screw  locks  it  securely  on  the  thread. 

A  hexagon  nut  tapped  and  split  through  on  one  side  may  be 
locked  on  threaded  work  by  clamping  under  the  screw  of  the 
common  lathe  dog,  thus  making  a  safe  driver  for  threaded  work. 


FIG.  308. 


FIG.  309. 


Very  light  work  is  frequently  driven  from  the  center  without 
the  use  of  a  dog,  thus  enabling  the  work  to  be  machined  all  over 
without  changing  ends.  When  an  exact  center  is  not  required 
in  the  finished  work  the  square  center  may  be  used  to  drive  it. 
Instead  of  making  a  round  center  bearing  on  the  live  center  end 
of  the  work,  a  pyramidal  or  square  center  is  formed  with  a  punch. 


IP 


§  o  1 


FIG.  310. 


FIG.  311, 


This  bearing  fits  over  a  square  live  center,  which  drives  the  work. 
A  square  center  is  a  difficult  one  to  keep  in  proper  shape. 

Another  method  of  driving  light  work  from  the  center  consists 
in  milling  a  thumb-nail  notch  in  the  live  center  end  of  the  work, 
as  shown  at  A  in  Fig.  309  and  using  a  live  center  with  a  driver, 
.as  shown  in  Fig.  310.  In  this  case  true  round  centers  are  used. 


214 


MODERN    MACHINE    SHOP    TOOLS. 


A  great  deal  of  work  done  between  centers  does  not  require  a 
dog,  as  a  face-plate  stud  or  driver  will  engage  some  part  of  the 
work  as  shown,  for  example,  in  the  case  of  a  pulley  in  Fig.  311. 
The  driver  in  such  cases  should  be  placed  as  far  from  the  center 
as  possible,  thus  making  it  firmer  and  steadier.  The  face- 
plate driver  should  be  a  stiff,  substantial  one.  A  bolt  strung  full 
of  nuts  and  washers  will  answer  after  a  fashion,  but  the  one 
shown  at  A  of  steel,  or  at  B  of  cast  iron,  in  Fig.  312,  will  be 
found  much  more  satisfactory.  Two  or  three  lengths  will  usual- 
ly meet  all  requirements.  Lathes  are  usually  provided  with  two 
face-plates,  one  of  large  diameter  and  one  of  small.  The  small 
plate  is  the  one  usually  used  for  driving  the  dog  on  work  held 
between  centers.  It  is  generally  a  round  plate  with  one  or  four 
notches.  The  plate  shown  in  Fi*r.  313  is  sometimes  used,  but 


PIG;  312. 


313- 


for  reasons  of  safety  is  not  as  good  as  the  round  one.  At  least 
one  notch  in  each  plate  should  extend  well  down  to  the  center, 
thus  enabling  the  use  of  the  smaller  dogs  when  operating  on 
light  work. 

Lathe  work  not  held  between  centers  can  be  classified  under 
the  head  of  center-rest,  carriage,  face-plate  and  chuck  work,  the 
distinction  between  the  two  last  classes  being  narrow.  Center- 
rest  work  includes  all  in  which  the  center-rest  carries  one  end 
of  the  work  and  the  live  spindle  the  other.  Carriage  work  in- 
cludes such  classes  as  are  operated  upon  by  a  rotating  cutter  while 
secured  to  the  carriage  of  the  lathe.  Chuck  and  face-plate  work 
covers  that  wide  range  of  operations  upon  work  rigidly  secured 
on  the  live  spindle. 

The  lathe  chuck  is  a  device  for  holding  work  more  firmly  and 
adjusting  it  more  accurately  than  is  conveniently  possible  when 
clamped  or  bolted  to  ,the  face-plate.  Chucks  are  classified  as  in- 


CHUCKS    AND   DRIVERS    FOR    LATHE    WORK. 


215 


dependent,  universal  and  combination.  In  Tig.  314  is  shown 
an  independent  four-jawed  lathe  chuck.  These  chucks  are  made 
with  two,  three  or  four  jaws  fitted  accurately  in  radial  ways  in  a 
substantial  plate  or  body.  Each  jaw  is  operated  independently 


FIG.  314. 

by  a  square-thread  screw.  The  jaws  may,  in  order  best  to  con- 
form to  the  character  of  the  work,  be  reversed.  The  two-jawed 
chucks  of  this  class  are  usually  employed  on  special  work;  the 


jaws  being  so  formed  as  to  receive  special  formed  faces  for  hold- 
ing work  of  plain  or  irregular  outline. 

The  universal  chuck,  an  example  of  which  is  shown  in  Fig. 
315.  is  usually  a  three-jawed  chuck,  although  they  may  be  had 


216 


MODERN    MACHINE   SHOP    TOOLS. 


with  two  or  four  jaws.  In  this  style  of  chuck  the  jaws  all  move 
together.  The  mechanism  of  the  three  and  four- jawed  universal 
chucks  usually  consists  of  a  geared  scroll  as  shown  in  front  and 
back  views,  Figs.  316  and  317.  In  the  two- jawed  universal  the 


FIG.  316. 


FIG.  317. 


jaws  are  connected  "by  a  right  and  left  screw.  The  universal 
chuck  is  used  mostly  on  milling  and  grinding  machine  heads, 
screw  machines,  cutting-off  machines  and  other  places  where  it 
is  desired  to  quickly  center  round  work.  When  new,  first-class 


FIG.  318. 


FIG.  319. 


universal  chucks  center  work  very  accurately ;  but  after  they  be- 
come somewhat  worn  they  should  not  be  relied  upon  for  exact 
centering. 

The  combination  chuck  involves  both  the  universal  and  inde- 


CHUCKS    AND    DRIVERS    FOR    LATHE    WORK. 


217 


pendent  characteristics,  as  by  a  slight  adjustment  it  may  quickly 
be  changed  from  one  to  the  other.  In  many  places  a  chuck  of 
this  character  is  very  well  adapted,  but  for  general,  every-day 
lathe  work  the  independent  four- jawed  chuck  is  more  suitable. 
A  combination  chuck  is  shown  front  and  sectional  views  in  Figs. 
318  and  319. 

A  combination  scroll  chuck  is  shown  in  section  at  X,  Fig. 


D/' 


FIG.  320. 


PTG.  321. 


218 


MODERN    MACHINE    SHOP    TOOLS. 


320,  with  an  end  view  of  the  jaw  A  and  carrier  C  at  Y.  In  this 
chuck  the  scroll  is  operated  by  a  spanner  wrench  engaging  the 
holes  D  D  in  its  back.  The  carriers  C  engage  the  scroll  and 
move  together.  The  screws  B  move  the  jaws  A  independently. 
A  universal  two- jawed  chuck  for  holding  firmly  bar  work  is 
shown  in  Fig.  321.  This  is  known  as  an  auxiliary  screw  chuck. 
The  details  of  the  jaws  are  shown  in  Fig.  322.  They  are  oper- 


ated  by  the  right  and  left  screw.,  which  engages  half  nuts  on  the 
side  of  the  jaws.  The  auxiliary  screw  passes  through  one  of 
the  jaws  on  the  opposite  side  from  the  main  screw  and  threads 
into  the  other  jaw.  After  closing  the  jaws  onto  the  work  with 
the  double  screw,  tightening  the  auxiliary  screw,  which  has  a 
fine  pitch  thread,  not  only  evens  up,  but  increases  the  pressure 
of  the  jaws  upon  the  work. 

In  Fig.  323  is  shown  a  face-plate  jaw.     These  jaws,  which 


FIG.  325. 


CHUCKS    AND   DRIVERS    FOR   LATHE    WORK. 


2IC> 


are  self-contained,  may  be  attached  to  a  face-plate,  and  as  such 
constitute  a  first-class  independent  chuck.  They  make  a  very 
satisfactory  substitute  for  the  larger  sizes  of  chucks,  and  are 
frequently  applied  to  very  large  face-plates. 

For  special  work,  as  the  finishing  of  cocks,  valves  and  fittings, 


FIG.  324. 

a  revolving  chuck  of  the  character  shown  in  Fig.  324  is  used. 
Special  jaws  hold  the  work,  and  a  suitable  indexing  arrangement 
provides  for  exact  division  and  rotation  about  an  axis  at  right 
angles  to  the  work  spindle. 


CHAPTER  XVII. 

LATHE    WORK — BETWEEN    CENTERS. 

One  of  the  first  and  simplest  jobs  the  beginner  does  in  the 
lathe  is  to  turn  a  plain  spindle.  He  can  begin,  even  on  this  job, 
to  exercise  his  judgment.  For  example,  he  is  given  a  bar  of 
round  steel  2  inches  in  diameter  and  is  to  make  a  plain,  straight 
and  true  spindle  iJ/$  inches  in  diameter  by  2  feet  long.  In  cut- 
ting this  bar  he  must  make  the  necessary  allowance  for  squaring 
up  the  ends.  If  cut  in  a  cutting-off  machine,  1-32  inch  will  do;  if 
in  the  power  hack  saw  1-16  inch  should  answer  if  the  saw  is 
running  reasonably  true,  while  y%  inch  or  even  *4  would  usually 
be  required  if  haggled  off  in  the  blacksmith  shop.  Having  cut 
the  bar  and  made  the  required  allowance  in  length,  he  next 
centers  it  with  punch  and  hammer. 

The  proper  locating  and  forming  of  centers  in  work  to  be 
machined  between  centers  is  of  importance.  When  considerable 
stock  is  to  be  removed  from  the  work,  and  it  is  therefore  not 
necessary  to  use  great  care  in  locating  the  center,  the  careful 
workman  can,  if  the  diameter  of  the  work  is  not  great,  usually 
spot  the  center  sufficiently  near  by  eye. 

When  the  ends  of  the  work  are  cut  reasonably  square,  the 
bell  center  punch  can  be  advantageously  used  as  shown  in  Fig. 
325.  The  punch  should  be  held  squarely  over  the  work  as  shown 
at  A.  If  the  work  is  not  sawed  reasonably  square  this  tool 
should  not  be  used,  as  it  will  not  show  a  true  center  as  illustrated 
at  B.  In  Fig.  326  is  shown  a  form  of  bell  centering  tool  in 
which  a  conical  recess  in  the  base  holds  the  lower  end  of  the 
work  true,  while  the  bell  which  moves  over  a  vertical  guide  lo- 
cates the  upper  center.  This  tool  is  very  nicely  adapted  to  the 
centering  of  a  large  variety  of  small  work.  The  caliper-dividers 
(hermaphrodite  calipers)  are  perhaps  more  used  for  this  work 
than  any  other  tool.  The  legs  are  adjusted,  as  shown  in  Fig. 
327,  to  approximately  the  radius  of  the  work,  which  has  previous- 
ly been  chalked  on  the  end  to  more  readily  show  the  marks. 
Three  or  four  arcs  are  then  scribed  from  about  equi-distant  points 
on  the  circumference  which  intersect,  as  shown  at  A  and  B.  The 


LATHE   WORK BETWEEN   CENTERS. 


221 


center  of  the  small  triangle  in  A  and  square  in  B  are  the  approxi- 
mate centers. 

For  work  of  large  diameter  the  center-head  square  as  shown 
in  Fig.  328  is  nicely  adapted.  A  line  is  scribed  along  the  straight 
edge  a  b ;  the  head  is  then  carried  about  one-fourth  around  the 
work  and  another  line  c  d  scribed ;  the  intersection  of  these  lines 
gives  the  center. 

By  placing  the  work  upon  a  plane  surface  the  center  can  read- 
ily be  found  by  means  of  the  surface  gauge,  as  shown  in  Fig.  329. 


FIG.  327. 


FIG.  326. 


FIG.  329. 


222 


MODERN    MACHINE    SHOP    TOOLS. 


Place  the  pointer  at  approximately  the  height  of  the  center  and 
scribe  four  lines,  the  work  being  rotated  about  90  degrees  for 
each  line.  The  center  of  the  small  inclosed  rectangle  will  be  the 
approximate  center  of  the  work.  A  pair  of  dividers  can  be  used 
in  place  of  the  surface  gauge  if  desired.  Having  located  and 
prick-punched  the  centers,  they  should  next  be  drilled  and 
reamed.  If  there  is  a  small  amount  of  stock  requiring  close 
centering,  the  work  should  be  placed  between  centers  and  rotated 
on  the  light  center-punch  marks  to  determine  whether  they  are 
sufficiently  accurate.  This  is  determined  by  giving  the  work  fast 
rotation  by  drawing  the  hand  over  it  quickly  and  holding  a  piece 
of  chalk  against  it  to  show  the  high  spots. 

If  too  badly  out,  the  punch  mark  can  be  drawn  over  the  re- 
quired amount  before  drilling  the  center.  The  form  of  center 
bearing  should  be  as  shown  at  B,  Fig.  330.  A  hole  of  from  1-32 


FIG.  330. 


to  34  mch  in  diameter,  depending  on  the  diameter  of  the  work, 
is  first  drilled/  and  then  countered  with  the  6o-degree  counter 
reamer  shown  at  A  and  B  in  Fig.  171.  The  hole  must  be  drilled 
deep  enough  to  prevent  the  lathe  center  from  reaching  the  bottom. 
At  C  in  Fig.  171  is  shown  a  most  excellent  combination  drill  and 
center  reamer  for  this  purpose.  The  drill  steadies  the  reamer 
and  insures  a  true  bearing  and  drilled  hole  of  proper  depth. 

The  drilled  hole  not  only  protects  the  delicate  point  of  the 
center,  but  serves  as  an  oil  reservoir  to  aid  in  lubricating  the 
center  bearing.  It  should  be  filled  with  oil  before  putting  the 
work  on  the  center. 

In  large  center  bearings  on  very  heavy  work  it  is  frequently 
desirable  to  cut  with  a  small  cape  chisel  one  or  more  narrow 
grooves  through  the  bearing  portion  to  facilitate  the  oiling  of  the 
center. 

Where  a  large  amount  of  centering  is  done,  a  machine  for 


LATHE    WORK BETWEEN    CENTERS.  223 

that  work  is  frequently  employed.  It  is  provided  with  a  self- 
centering  chuck  for  the  work,  which  obviates  the  necessity  of 
previously  center-marking  it. 

He  now  squares  off  the  ends  with  a  side  cutting  tool,  and  how 
easily  he  gets  them  square  to  the  very  center  by  slacking  back 
slightly  on  the  tail  spindle  and  allowing  the  tool  to  cut  into  the 
center.  He  must  be  particular  about  getting  the  bar  to  exact 
length  in  this  operation,  and  when  finally  to  length  the  ends  must 
look'  as  shown  at  B  in  Fig.  330.  To  leave  an  end  as  shown  at 
C  is  unpardonable,  even  on  the  roughest  kind  of  work.  When 
left  as  shown  at  B  a  reliable  center  can  be  had  at  any  time  should 
it  ever  become  necessary  to  place  the  spindle  between  centers 
again. 

He  should  next  rough  to  within  about  1-32  inch  of  the  finished 
diameter  for  a  length  of  from  three  to  four  inches  from  the  tail 
center.  In  doing  this  the  center  bearing  at  that  end  becomes 
worn  down  to  a  nice,  true  bearing.  The  work  is  now  changed 
end  for  end  and  the  balance  first  roughed  down  and  then  finished. 
It  should  be  here  noted  that  no  part  of  the  work  should  receive 
its  final  finishing  cut  until  it  has  all  been  roughed  over.  The 
reasons  for  this  are,  first,  that  the  centers  should  be  worn  down 
to  true  bearings,  and  second,  because  of  the  springing  due  to 
removing  the  fiber  strains  in  the  metal.  If  a  part  be  given  the 
final  finish  before  the  balance  is  roughed  down,  that  part  will 
usually  be  found  out  of  true  after  the  last  roughing.  Not  only 
is  this  the  case  with  the  rolled  metals,  but  with  the  cast  as  well, 
where  the  removal  of  the  skin  or  scale  usually  causes  the  work 
to  change  somewhat  in  form. 

The  required  quality  and  truth  of  the  finished  surface  must 
determine  the  number  of  cuts  to  take.  For  the  roughest  work 
a  single  cut  will  frequently  do,  and  for  general  work  two  cuts, 
the  first  a  roughing  leaving  only  enough  for  a  finishing  cut.  The 
latter  cut  should  always  be  a  light  one.  When  a  very  nice,  true 
surface  is  desired  three  cuts  are  advisable ;  a  roughing,  a  sizing 
and  a  finishing  cut. 

In  turning  the  above  bar  the  young  mechanic  should  learn  a 
lesson  in  cutting  speeds.  Mild  steel  can  be  machined  at  from 
20  to  TOO  feet  cutting  speed  per  minute,  depending  on  its  hard- 
ness and  the  quality  of  the  cutting  tool. 

The  beginner  usually  runs  way  below  speed,  and  as  he  has 
no  experience  upon  which  to  base  his  judgment  in  speeding  the 


224  MODERN    MACHINE    SHOP    TOOLS. 

work,  he  should  make  a  simple  calculation  in  each  case  until  his 
eye  tells  him  the  proper  speed  without  figuring  it. 

As  the  circumference  of  the  work  is  approximately  three  times 
the  diameter,  he  would  in  the  present  case  have  the  work  mov- 
ing to  the  tool  about  six  inches  per  revolution.  At  a  cutting 
speed  of  say  25  feet  per  minute,  the  work  should  make  about 
fifty  revolutions  per  minute.  Chalking  a  spot  on  the  face-plate 
and  counting  the  revolutions  will  determine  quickly  whether  or 
not  the  speed  is  correct. 

This  matter  of  speed  is  of  very  great  importance,  not  only  in 
its  effects  upon  the  output  of  the  lathe,  but  upon  the  workman 
himself,  as  he  quickly  becomes  tuned  with  his  machine  and  loses 
that  snap  and  vigor  at  his  work  which  comes  from  seeing  every- 
thing move  along  at  a  quick,  business-like  pace. 

The  young  mechanic  should  familiarize  himself  at  the  begin- 
ning with  all  the  details  of  construction  and  manipulation  of  the 
lathe  itself.  He  will  necessarily  do  work  slowly  at  first,  but  he 
must  learn  accuracy  from  the  beginning.  The  speed  will  come 
as  he  improves  in  skill  and  gains  in  confidence. 

He  must  learn  early  the  power  of  the  machine,  the  strength 
and  wearing  qualities  of  the  cutting  tools  and  the  strength  of  the 
materials  upon  which  he  operates.  He  will  then  not  overtax  the 
machine  and  break  or  injure  the  tools  and  work;  neither  will  he 
take  three  cuts  over  a  piece  of  work  when  two  would  have  an- 
swered quite  as  well. 

If  the  surface  is  to  be  a  polished  one,  he  must  make  some  al- 
lowance for  filing  and  finishing  with  emery.  This  is  a  matter  of 
judgment,  and  the  beginner's  judgment  is  usually  poor,  as  lie 
leaves  altogether  too  much  to  remove  with  the  file,  which  takes 
up  time  and  injures  the  truth  of  the  work.  It  is  very  difficult  to 
file  much  on  rotating  work  and  keep  it  cylindrically  true.  The 
finishing  cut  should  therefore  leave  the  surface  smooth,  true  and 
within  one  to  five  thousandths  of  an  inch  of  finished  size,  de- 
pending on  the  degree  of  accuracy  required. 

When  the  spindle  is  very  long  and  its  diameter  relatively 
small,  it  becomes  necessary  to  support  it  at  some  intermediate 
point  or  to  provide  some  form  of  support  immediately  back  of 
the  cutting  tool,  as  otherwise  it  would,  owing  to  its  own  weight 
and  the  pressure  against  the  cut,  spring  excessively,  causing  it 
to  chatter  and  leave  an  untrue  surface.  In  such  a  case,  the  cut 
would  have  to  be  very  light  to  prevent  the  work  from  bending 


LATHE    WORK BETWEEN    CENTERS. 


225 


or  climbing  up  on  the  point  of  the  tool,  which  is  a  very  exasperat- 
ing accident  that  frequently  happens  even  when  the  greatest  care 
is  exercised,  and  it  usually  results  in  spoiling  the  work. 

The  center  or  steady  rest  in  its  general  form  is  shown  at  A  in 
Fig.  331.  Its  construction  is  plainly  seen  from  the  figure.  The 
foot  is  clamped  to  the  shears  of  the  lathe  at  any  convenient  point, 
and  the  three  sliding  jaws  are  so  secured  that  they  can  be  ad- 
justed upon  a  portion  of  the  work's  length  that  has  previously 
been  turned  true  and  smooth.  If  the  bar  is  to  be  turned  over  its 
entire  length,  this  spot  is  usually  taken  just  off  the  middle  point 


FIG.  331. 

and  a  little  closer  to  the  live  center  than  the  dead  one.  This  en- 
ables the  operator  to  turn  from  the  dead  center  toward  and  some- 
what past  the  middle.  The  work  can  then  be  reversed,  the  jaws 
adjusted  to  the  turned  portion  and  the  balance  of  the  spindle 
machined.  Truing  the  spot  is  usually  slow,  as  light  cuts  must 
be  taken  in  order  to  get  a  round  section  that  is  concentric 
with  the  axis  of  rotation.  It  is  also  difficult  to  properly  set  the 
jaws  of  the  center  rest  upon  the  spot  without  throwing  the 
work  center  out  of  the  line  between  the  centers  of  the  lathe.  It 
is  usually  best  to  adjust  the  two  bottom  jaws  first  and  thus 


226 


MODERN    MACHINE    SHOP    TOOLS. 


relieve  the  work  of  the  deflection  due  to  its  own  weight.  The 
jaws,  if  set  too  tight  upon  the  work,  will  heat  and  score  it. 
Oil  should  always  be  used  and  the  ends  of  the  jaws  kept  in  good 
condition.  If  the  work  is  to  be  machined  only  at  points  on 
its  length,  then  the  center  rest  should  be  set  as  near  as  possible 
to  the  point  where  the  work  is  being  done,  and  thus  give  the 
greatest  amount  of  rigidity. 

Frequently  it  becomes  necessary  to  steady  a  bar  for  turning 
that  is  not  and  cannot  be  made  round  at  the  point  where  the 
center  rest  is  to  be  applied.  In  such  cases  the  device  shown  in 
Fig.  332,  and  commonly  known  as  a  cat  head,  may  be  used.  It  is 


FIG.  332. 

simply  a  collar  turned  round  on  its  outer  surface  and  provided 
with  suitable  set  screws  for  centering  it  upon  the  work.  This 
gives  a  round  bearing  which,  as  before,  is  made  to  run  within  the 
jaws  of  the  center  rest.  The  cat  head  must  be  so  adjusted  that 
it  runs  perfectly  true  on  the  outside  or  otherwise  the  work  will 
not  run  true  when  the  head  is  removed  after  turning.  The 
effect  of  crowding  the  work,  with  one  of  the  jaws  out  of  its  true 
axis  of  rotation,  is  to  turn  the  work  tapering.  Thus,  if  the  work 
is  crowded  by  the  center  rest  toward  the  tool,  It  will  be  turned 
smaller  in  the  center  than  at  the  ends  and  in  like  manner  larger 
at  the  center  if  crowded  away  from  the  tool.  Vertical  motion 
does  not  affect  the  diameter  to  so  great  an  extent,  since,  if  the 
tool  is  set  at  the  height  of  the  center,  the  work  can  be  raised  or 
depressed  quite  a  distance  without  making  much  change  in  the 


LATHE   WORK BETWEEN   CENTERS. 

diameter.  If,  however,  the  tool  sets  above  or  below  the  center, 
a  material  taper  will  be  given  to  the  work.  For  example,  if 
the  tool  sets  above  the  center  and  the  work  is  depressed  at  the 
center  rest,  it  will  be  turned  larger  in  diameter  at  the  rest  than 
at  the  dead  center.  Very  often  it  is  desirable  to  support  the  work 
right  at  the  tool  for  the  entire  length  of  the  cut.  This  is  ac- 
complished by  using  the  follow  rest,  an  example  of  which  i? 
shown  at  B  in  Fig.  331.  It  is  quite  similar  in  its  most  general 
form  to  the  center  rest,  having  two  jaws,  one  behind  and  the 
other  on  top  of  the  work.  It  is  secured  direct  to  the  carriage  and 
consequently  moves  with  the  tool.  If  the  work  is  in  the  rough, 
the  rest  follows  after  the  tool,  but  if  it  has  been  previously  trued, 
the  rest  may  be  set  ahead  of  the  tool.  It  is,  however,  usually 
preferable  to  have  the  rest  follow  rather  than  lead  the  cutting- 
tool.  For  work  of  small  diameter  a  single  jaw  with  a  V-end 
serves  well. 

The  producing  of  satisfactory  results  in  the  use  of  the  follow 
rest  requires  good  judgment  on  the  part  of  the  operator.  It 
should  be  set  as  soon  as  possible  after  the  cut  has  left  the  dead 
center  and  while  the  work  is  rigid  and  true.  Any  irregularities 
in  the  work  surface  over  which  the  follow  rest  passes  serve  to 
reproduce  these  same  irregularities  throughout  the  length  of 
the  work,  and  it  is,  therefore,  very  important  to  start  exactly 
right.  In  the  cutting  of  threads  on  long  light  rods  the  follow 
rest  is  indispensable.  It  is  also  of  value  in  steadying  work  that 
is  being  operated  upon  by  a  cutting-ofl  tool.  It  is  superior  to 
the  center  rest  for  this  purpose,  inasmuch  as  it  can  be  set  so 
much  closer  to  the  point  where  the  cut  is  being  taken. 

An  example  of  center  rest  work  is  shown  in  Fig.  333.  Here, 
as  is  frequently  the  case,  it  is  required  to  operate  on  the  end  of 
the  work  which  precludes  the  possibility  of  running  that  end  on 
the  center.  The  center  rest  carries  the  outer  end,  the  tail  stock 
is  moved  back  out  of  the  way  and  the  carriage  is  given  ample 
room  to  get  the  tool  at  the  work  surface.  The  work  must  be 
firmly  secured  to  the  head  spindle.  When  a  center  bearing  can 
be  had  in  that  end  of  the  work,  it  is  best  to  carry  it  on  the  live 
center.  This  requires  some  method  for  clamping  it  to  the  face- 
plate to  prevent  it  from  drawing  off  the  center.  When  the  work 
has  a  convenient  shoulder  near  the  outer  end,  the  inner  faces  of 
the  jaws  of  the  center  rest  may  be  made  to  bear  against  the 
shoulder  and  thus  prevent  the  work  from  drawing  away  from 


228 


MODERN    MACHINE    SHOP    TOOLS. 


the  live  center.  A  collar  can  be  clamped  on  the  work  to  accomp- 
lish this  result,  but  this  method  is  not  satisfactory  except,  per- 
haps, in  the  case  of  very  light  work,  as  the  center  rest  is  not  rigid 
against  a  side  pressure  and  the  cramp  of  the  dog  or  driver  is 
quite  certain  to  crowd  the  work  off  the  center.  A  clamp,  as 
shown  in  Fig.  334,  slipped  over  the  work  behind  the  dog  and 
drawn,  by  means  of  bolts,  firmly  against  the  face-plate  will  be 
found  quite  satisfactory.  It  is  necessary  that  the  clamp  be 
drawn  up  squarely,  as  otherwise  the  truth  of  the  work,  especially 
if  light,  will  be  affected. 

In  cases  where  there  is  no  center  bearing  in  the  live  center 
end  of  the  work,  and  one  cannot  conveniently  be  arranged  for, 
that  end  can  be  carried  in  a  chuck.  If  the  chuck  is  an  inde- 


> 

g 

3 

... 

t 

h 

41      gjf 

P 

/ 

j  — 

; 

r   ' 

J                               /- 

1 

- 

FIG.  333- 


FIG.  334. 


pendent  one,  the  work  must  be  very  carefully  centered  in  it.  If 
a  universal  chuck  is  used  and  exact  centering  of  the  work  is  re- 
quired, it  is  equally  necessary  to  test  the  truth  of  the  work,  as 
universal  chucks,  after  being  somewhat  worn,  lose  their  accuracy 
for  exact  centering.  The  work  should  be  caught  close  to  the 
ends  of  the  jaws,  except  in  cases  where  the  jaws  and  surface  of 
the  work  gripped  are  known  to  be  absolutely  true;  otherwise  the 
outer  end  of  the  work  will  be  thrown  out  of  the  center  of  rota- 
tion and,  if  brought  back  by  the  center  rest,  a  spring  in  the  length 
of  the  work  must  result.  It  is,  in  any  case,  difficult  to  set  the 
center  rest  so  that  it  will  hold  the  axis  of  the  work  exactly  coin- 
cident with  the  line  of  the  centers.  If  not  so  held,  the  work  will 
run  true,  but  all  cuts  will  be  tapering.  If  it  is  much  out  in  this 
adjustment,  it  will  cause  the  live  center  end  of  the  piece  being 
machined  to  work  on  the  centers  or  in  the  chuck  jaws,  the  usual 


LATHE    WORK BETWEEN    CENTERS. 


229 


result  being  the  loss  of  the  grip.     The  stiffer  the  work,  the  more 
noticeable  this  action. 

.  The  turning  of  external  tapers  can  be  accomplished  in  several 
different  ways.  As  above  indicated,  in  center  rest  work,  if  the 
rest  holds  the  end  of  the  work  so  that  its  center  is  back  or  ahead 
of  the  line  of  centers,  tapered  work  results.  In  like  manner, 
where  the  work  is  carried  on  both  centers,  if  the  dead  center  is 
moved  across  the  bed,  the  center  line  of  'the  work  will  be  at  an 
angle  with  the  direction  of  motion  of  the  carriage»and  tool,  and 
tapered  work  results.  As  all  engine  lathes  are  provided  with  a, 
set-over  adjustment  in  the  tail-stock,  this  method  of  turning  tapers 
is  always  available.  As  the  amount  of  side  adjustment  is  limited 
to  a  small  range,  only  slight  tapers  can  be  produced  in  this  man- 
ner, and  especially  so  in  cases  where  the  work  is  long.  Thus,  if 
the  tail  center  can  be  set  over  one  inch  and  the  work  is  four  feet 
long,  then,  as  shown  in  Fig.  335,  it  will  be  turned  two  inches 


FIG.  335. 

smaller  at  the  dead  center  end  than  at  the  live  center  end,  which 
would  give  a  taper  of  one-half  inch  per  foot.  If  the  work  was 
one  foot  long,  as  shown  by  the  dotted  lines,  it  would  have  a  taper 
of  two  inches  per  foot.  The  above  indicates  the  method  for 
determining  the  amount  to  set  the  tail  center  over  to  produce  any 
taper  per  foot  within  the  limits  of  the  adjustment.  Thus,  if 
the  work  is  eighteen  inches  long  and  a  taper  of  five-eighths  of 
an  inch  per  foot  is  required,  at  one  foot  the  offset  would  be  one- 
half  the  required  taper  or  five-sixteenths  of  an  inch,  and  at  one 
.and  one-half  feet  it  would  be  11/2X5-16,  or  15.32  of  an  inch. 

This  is,  of  course,  only  an  approximate  method  for  determin- 
ing the  proper  amount  of  set-over,  as  the  exact  amount  must,  in 
nearly  every  case,  be  found  by  trial.  It  will,  however,  serve  bet- 


230 


MODERN    MACHINE  .SHOP    TOOLS. 


ter  than  a  guess  for  the  first  trial.  The  principal  objection  to 
this  method  of  taper  turning  is  that  the  centers  of  the  lathe  no 
longer  point  toward  each  other,  and  the  center  bearings  in  the 
work  do  not,  therefore,  bear  properly  upon  them.  This  fre- 
quently causes  excessive  wear  on  the  bearings  and  sometimes 
throws  the  work  out  of  true.  The  ends  of  the  work  must  be 
faced  off  perfectly  square,  or  otherwise  the  work  will  be  sure 
to  run  somewhat  out  when  held  on  offset  centers.  Since  in  this 
class  of  turning  the  work  does  not  stand  at  right  angles  to  the 

face-plate,  it  is  necessary  to  al- 
low for  some  in-and-out  motion 
for  the  arm  of  the  dog  or  driver 
through  the  face  plate.  When 
the  lathe  is  provided  with  taper 
attachment,  as  shown  in  Fig.  336^ 
external  tapers  may  be  turned 
without  offsetting  the  dead  cen- 
ter. This  leaves  the  true  bear- 
ings on  the  centers  and  does  not 
necessitate  the  difficulty  of  hav- 
ing to  adjust  the  dead  center  for 
parallel  turning  each  time  after  a 
taper  job  has  been  done.  Taper 
attachments  are  given  a  much 
wider  range  than  can  be  obtained 
by  offsetting  the  center  and  are 
equally  as  useful  in  boring  tap- 
ered holes  as  in  turning  external  tapers. 

In  all  taper  attachments  the  mechanism  is  such  as  to  operate 
the  tool  rest  direct  from  a  guide  set  at  any  required  angle,  within 
its  limits,  with  the  shears  of  the  lathe  and  independent  of  the 
cross-feed  screw,  yet  at  the  same  time  retaining  the  in-and-out 
adjustment  of  the  cross-feed  screw.  As  several  parts  and  con- 
sequent joints  are  required  in  such  combinations,  a  considerable 
amount  of  back  lash  usually  exists.  The  effect  of  this  back  lash 
is  to  let  the  tool  start  on  a  parallel  cut  until  the  back  lash  is 
taken  up,  when  it  starts  off  on  the  required  taper.  This  can 
usually  be  overcome  by  carrying  the  tool  enough  beyond  the  end 
of  the  work  to  allow  the  slack  to  take  up  by  the  time  the  tool 
is  brought  up  to  the  cut.  It  will  be  understood  that  it  is  not 
necessary  to  let  the  feed  bring  the  tool  up  to  the  cut,  as  it  can 


FIG.  336. 


LATHE   WORK BETWEEN    CENTERS.  23! 

be  advanced  quickly  by  hand,  the  only  point  being  to  carry  it  far 
enough  to  take  up  the  slack  by  the  time  the  tool  reaches  the 
work.  On  work  of  small  diameter,  where  the  tool  strikes  the 
side  of  the  center  if  moved  beyond  the  end  of  the  work,  the  back 
lash  can  generally  be  taken  up  by  pulling  out  or  pushing  sharply 
in  on  the  tool  post,  depending  on  the  direction  of  taper  the  at- 
tachment is  set  to  turn.  Thus,  if  it  is  set  to  turn  an  increasing 
taper  from  the  dead  center  toward  the  live,  the  angle  of  the 
guide  will  be  such  that  its  end  nearest  the  head  stock  will  be  the 
closest  to  the  shears  and  the  inside  face  of  the  block  will  be  forc- 
ing the  tool  back  from  the  center  of  rotation.  It  would  then  be 
necessary,  in  taking  up  the  back  lash  at  the  beginning  of  the  cut, 
to  push  the  tool  toward  the  center.  The  maximum  range  usual- 
ly given  the  taper  attachment  is  four  inches  per  foot. 

It  is  seldom  necessary  to  turn  or  bore  steeper  tapers  than  can 
be  bored  with  the  taper  attachment.  "\Yhen,  however,  such  are 
required,  a  lathe  with  a  compound  rest  can  be  used.  Examples 
of  the  compound  rest  are  shown  in  Figs.  242  and  243.  Its  con- 
struction is  such  as  to  allow  the  upper  slide  which  carries  the  tool 
to  be  set  and  secured  at  any  angular  position  with  the  cross  slide, 
thus  enabling  the  turning  or  boring  of  any  taper.  Although  the 
range  is  small,  steep  tapers  are  usually  short,  and  it  is  conse- 
quently seldom  that  the  tool  must  be  reset  in  turning  any  ordi- 
nary taper. 

\Yhen  a  lathe  is  to  be  kept  continually  on  taper  work,  a  posi- 
tive taper-turning  lathe  is  superior  to  one  having  a  taper  attach- 
ment. In  lathes  of  this  character  the  head  and  tail  stocks  are 
mounted  upon  an  auxiliary  bed  or  platen  which  is  pivoted  at  the 
center  and  clarnped  at  each  end  of  the  main  bed.  The  axial 
alignment  of  the  head  and  tail  spindles  is  maintained,  thus  allow- 
ing the  work  to  bear  squarely  upon  the  centers.  A  suitable 
graduation  at  one  end  of  the  bed  enables  the  operator  to  set  the 
line  of  centers  at  any  desired  angle,  within  the  range  of  the  ma- 
chine, with  the  shears  and  line  of  travel  of  the  tool.  This  ar- 
rangement not  only  possesses  all  the  good  features  of  the  taper- 
turning  attachment,  but  eliminates  the  troubles  arising  from  back 
lash. 

In  all  taper  turning  it  is  necessary  to  set  the  point  of  the 
cutting  tool  at  the  height  of  the  center  in  order  to  obtain  the 
taper  indicated  by  any  setting.  If  the  tool  is  set  above  or  below 
center,  the  resulting  taper  will  be  less  and  slightly  concave. 


2$2  MODERN    MACHINE    SHOP    TOOLS. 

In  turning  an  external  taper  to  fit  a  tapered  bore  the  correct 
taper  must  be  obtained  before  the  work  is  brought  down  to  exact 
size.  In  making  the  preliminary  setting  for  the  first  cut  too 
great  rather  than  too  small  a  taper  should  result,  as  the  measure- 
ment will  be  taken,  at  the  small  end,  and  if  the  taper  is  too  small 
the  work,  while  large  enough  at  the  small  end,  will-  be  under  size 
at  the  large  end.  In  getting  the  exact  taper  the  work  should  be 
tried  in  the  bore  after  each  cut.  As  long  as  the  difference  in 
taper  is  considerable  the  sense  of  feeling  may  be  depended  upon 
to  determine  which  way  to  vary  the  taper  in  order  that  it  may 
correspond  with  the  taper  of  the  bore.  When  too  close  to  note 
the  error  by  that  means,  draw  three  lines  with  chalk  lengthwise 
on  the  surface  and  at  approximately  equal  distances  apart.  Place 
the  work  in  the  bore  and  turn  it  carefully  through  a  complete 
revolution.  Upon  removing  it,  if  the  chalk  marks  have  been 


H 


FIG.  337. 

rubbed  apparently  equal  their  entire  length,  the  taper  is  correct. 
If,  however,  the  marks  have  rubbed  at  one  end  and  not  at  the 
other,  a  further  adjustment  must  be  made  and  another  cut  taken. 
For  very  accurate  work  a  marking  of  Prussian  blue  is  used  in- 
stead of  chalk.  It  is  applied  with  the  finger  and  rubbed  down 
until  the  coating  is  very  thin.  In  testing,  the  work  should  be 
turned  in  the  opposite  direction  to  that  in  which  it  rotated  in 
machining,  as  the  feed  of  the  tool  leaves  a  thread-like  surface 
which  tends  to  worm  the  work  tight  into  the  tapered  bore. 

After  the  correct  taper  has  been  obtained,  the  work  can  be 
turned  down  to  exact  size,  calipering  at  the  small  end. 

What  is  commonly  known  as  offset  turning  between  centers 
is  illustrated  by  the  example  shown  in  Fig.  337.  In  this  case  it 
is  required  to  turn  the  pin  of  the  crank  shaft,  the  shaft  proper 
having  been  turned  or  preferably  roughed  down  nearly  to  size. 


LATHE    WORK liETWEEX    CENTERS.  233 

The  offsets  are  at  a  distance  from  the  center  of  the  shaft  equal 
to  one-half  of  the  required  throw  of  the  crank.  By  means  of  a 
surface  gauge  and  plane  table  upon  which  the  crank  rests,  the 
centers  of  the  shaft,  the  offset  centers  and  the  center  of  the  crank 
pin  are  brought  into  the  same  plane.  By  now  placing  the  shaft 
on  the  offset  centers,  the  center  of  the  crank  pin  falls  in  the 
center  of  rotation,  and  by  means  of  a  long  tool  that  will  reach 
the  pin  through  the  throat  of  the  crank,  it  is  readily  turned. 

A  sufficient  counterweight  should  be  placed  on  the  face-plate 
opposite  the  shaft  to  balance  it  and  thus  make  the  lathe  rotation 
smooth.  As  it  is  not  possible  to  use  a  center  rest  on  work  of 
this  kind,  and  as  danger  of  springing  the  shaft  is  great,  consider- 
able care  must  be  exercised  in  turning  the  pin.  In  turning  the 
shaft,  a  center  rest  can  be  used.  It  is  usual  to  place  a  block 
firmly  in  the  throat  opposite  the  ends  of  the  shaft  to  prevent 
springing  the  arms  together.  The  finishing  cut  should  be  a 
light  one  taken  with  the  block  removed  and  the  centers  very 
lightly  adjusted,  thus  insuring  a  true  running  shaft  when  com- 
pleted. Eccentric  turning  comes  under  exactly  the  same  head. 
The  center  of  the  eccentric,  however,  usually  comes  inside  the 
bore  and  the  offset  centers  can  therefore  be  placed  in  the  mandrel 
itself. 

\Yhen  a  number  of  crank  pins  are  to  be  turned,  a  face-plate 
fixture  and  floating  tail  center  offset,  as  shown  in  Fig.  338,  proves 
a  very  efficient  tool.  The  shafts  are  all  turned  to  the  same  diam- 
eter, which  should  be  enough  over  size  to  allow  for  a  finishing  cut 
after  the  pins  are  finished.  As  the  shaft  is  firmly  held  in  the 
long  jaw,  a  much  heavier  cut  can  be  taken  over  the  pin  than  when 
held  as  shown  in  Fig.  337.  The  tail  offset  carries  an  eccentric 
or  floating  center  which  can  be  adjusted  to  the  tail  center  and 
clamped  in  position. 

In  screw  cutting  between  centers  the  proper  change  gears  are 
adjusted  on  the  lathe  to  give  the  required  pitch,  as  described  in 
Chapter  XIII.  The  cutting  tool  is  firmly  clamped  in  the  tool 
post  with  its  center  line  at  right  angles  to  the  axis  of  the  work. 
The  center  gauge,  shown  in  Fig.  97,  may  be  advantageously  used 
for  setting  the  tool.  The  height  of  the  tool  should  be  such  that 
its  top  face  lies  in  a  radial  line  drawn  from  the  center  of  the  work. 
If  set  above  or  below  this  position  the  angle  of  the  thread  cut 
will  not  correspond  with  the  angle  of  the  tool,  nor  will  the  sides 
of  the  threads  be  straight.  The  nut  is  next  closed  onto  the 


234  MODERN    MACHINE    SHOP    TOOLS. 

lead  screw  and  the  tool  set  in  for  the  first  cut.  If  the  thread  to- 
be  cut  is  right-handed,  the  lead  screw  is  given  right-hand  rota- 
tion with  the  lathe  spindle  running  forward,  thus  leading  the 
carriage  and  tool  from  the  tail  spindle  toward  the  head.  When 
the  thread  is  to  be  left-handed,  the  direction  of  rotation  of  the 
lead  screw  is  reversed,  the  tool  is  set  at  the  face-plate  end  of  the 
work  and  the  lead  is  from  the  live  toward  the  dead  center.  For 
each  succeeding  cut  the  tool  is  advanced  slightly  until  the  full 
depth  of  the  thread  has  been  formed.  The  first  cuts  should  be  as 
heavy  as  the  nature  of  the  work  will  permit.  The  last  cuts. 


FIG.  338. 

should  be  light,  in  order  that  the  thread  may  be  finished  smooch 
and  true.  If  the  threads  are  being  cut  on  steel  or  wrought-iron, 
a  liberal  supply  of  thread-cutting  oil  should  be  kept  constantly 
at  the  cutting  edges. 

The  amount  of  tool  advance  for  each  cut  is  usually  gauged  by 
means  of  a  graduated  dial  on  the  lathe  cross-feed  screw,  or  a 
threaded  stop  screw  which  can  be  turned  back  slightly  for  each 
cut,  thus  allowing  the  tool  to  be  set  in  a  corresponding  amount. 

When  thoroughly  practised  in  thread-cutting  work  the  oper- 
ator usually  gauges  the  amount  of  each  cut  instinctively  by  the 
position  of  the  cross-feed  screw  crank. 


LATHE   WORK BETWEEN    CENTERS. 


235 


After  each  cut  over  the  work,  it  is  necessary  to  draw  the  tool 
out  from  the  cut  before  reversing  the  work  for  returning  the 
tool  to  the  point  of  starting.  This  is  due  to  the  back  lash  in  the 
long  train  connecting  the  tool  and  spindle.  The  tool  should  be 
carried  slightly  beyond  the  point  of  starting  in  order  that  the 
back  lash  will  be  taken  up  by  the  time  it  enters  the  cut.  If  it 
become  necessary  for  any  reason  to  remove  the  tool  from  the 
tool  post  before  the  thread  is  completed,  great  care  must  be  ex- 
ercised in  resetting  it.  The  lathe  should  be  run  forward  one  or 
two  revolutions,  which  takes  up  the  back  lash  and  starts  the 
carriage  forward,  after  which  the  tool  can  be  set  to  the  groove 
already  cut.  After  the  thread  is  started,  the  driver  should  not  be 
removed,  and  if  the  work  is  removed  for  testing,  it  is  necessary 
to  put  it  back  on  centers  with  the  dog  or  driver  engaging  the 
same  notch  in  the  face-plate.  For  this  reason  it  is  preferable  to 
use  for  threading  a  small  single-notch  face-plate.  If  the  work 
is  long  and  springy,  the  follow  rest  B,  Fig.  331,  should  be  used  to 
support  it. 

In  cutting  double  threads  it  becomes  necessary  after  the  first 
thread  has  been  completed  to  advance  the  cutting  tool  an  amount 
equal  to  one  half  the  pitch,  as  shown  in  Fig.  339.  This  may 


FIG.  339. 


FIG.  340. 


readily  be  accomplished  as  follows :  In  lathes  where  the  ratio 
between  stud  and  spindle  is  one,  mark  a  tooth  on  the  stud  gear 
and  the  corresponding  tooth-space  on  the  intermediate  gear. 
Drop  the  intermediate  gear  out  of  mesh  and  turn  the  spindle  until 
one-half  of  the  number  of  the  teeth  in  the  stud  gear  have  passed 
the  marked  space  on  the  intermediate  gear.  Throw  the  gears 
into  mesh  and  proceed  with  the  cutting.  It  is,  of  course,  neces- 
sary that  the  stud  gear  have  an  even  number  of  teeth  in  the  above 
case.  If  the  ratio  between  stud  and  spindle  is  other  than  one. 


MODERN    MACHINE    SHOP    TOOLS. 


the  stud  gear  must  be  rotated  an  amount  proportional  to  that 
ratio.  The  -better  and  more  convenient  method,  however,  is  to 
have  milled  notches  in  the  face-plate  accurately  indexed.  Re- 
move the  worh  and  place  the  tail  of  the  dog  or  driver  in  the 
notch  diametrically  opposite  the  one  in  which  it  was  while  the 
first  thread  was  being  cut.  For  triple  and  quadruple  threads  the 
above  methods  are  equally  applicable. 

As  the  common  thread-cutting  tool  cannot  be  given  any  top 
rake  it  is  not  free  cutting.  The  strain  upon  it  is  consequently 
great,  and  it  at  once  becomes  a  hard  tool  to  keep  sharp  and  in 
proper  condition.  When  the  lathe  has  a  compound  rest  the  tool 
shown  in  Fig.  340  may  be  used  for  cutting  V  threads.  The  com- 
pound rest  is  set  at  60  degrees  with  the  axis  of  the  work  as  shown 
in  Fig.  341,  and  the  tool  set  with  the  thread  gauge  in  the  usual 


FIG.  341. 

manner.  The  tool  is  given  top  rake  and  cuts  a  clean  chip  from 
the  end  a,  it  being  advanced  to  the  work  by  the  compound  slide. 

For  cutting  square  threads,  the  tool  used  resembles  a  cutting- 
off  tool  with  the  plane  of  the  blade  set  at  the  angle  of  the  pitch 
of  the  thread,  as  shown  in  the  end  view,  Fig.  342.  The  amount 
of  this  angle  varies  for  all  pitches  and  diameters,  but  the  side 
clearance  is  usually  sufficient  to  allow  some  variation  in  diameters 
without  changing  the  center  angle. 

For  all  classes  of  work  on  center  it  is  very  important  that  the 
centers  be  kept  true  and  smooth.  They  are  turned  in  the  head- 
spindle  to  the  correct  angle,  tempered  and  ground.  The  tail  or 


LATHE   WORK BETWEEN   CENTERS. 


237 


dead  center  is  ground  first  and  the  live  center  is  then  ground  in 
place,  and  preferably  not  removed  from  its  bearing  after  grind- 
ing. The  live  center  should  be  marked  close  up  to  the  nose  of 
the  spindle  with  a  corresponding  mark  on  the  spindle,  thus  mak- 
ing it  possible  to  always  put  it  back  in  the  same  position. 

Before  putting  centers  into  their  bearings,  both  surfaces 
should  be  carefully  wiped  clean  and  dry. 

In  Fig.  343  is  shown  a  form  of  lathe  center  that  can  be  very 
easily  kept  in  shape  without  excessive  grinding. 

In  most  threading  work  on  the  lathe  the  nut  is  not  opened 
from  the  lead  screw  after  the  thread  is  once  started ;  the  lathe 
after  each  cut  being  reversed  and  the  tool  run  back  to  the  be- 


1 


FIG.  342. 


G  round 


FIG.   343. 

ginning  of  the  thread.  When  the  thread  is  a  long  one  much  time 
is  lost  by  following  this  method,  and  the  nut  should  be  disengaged 
and  the  tool  moved  quickly  back  to  the  beginning  of  the  thread. 
In  all  cases  where  the  number  of  threads  per  inch  being  cut  is  a 
multiple  of  the  number  of  threads  per  inch  on  the  lead  screw, 
they  may  be  cut  simply  by  engaging  the  nut  at  any  position  on 
the  screw ;  thus,  if  the  lead  screw  has  six  threads  per  inch,  6, 
12,  18,  24,  30,  etc.,  threads  per  inch  may  be  cut  by  catching  the 
thread  at  any  point,  it  being  impossible  to  catch  the  tool  in  any 
position  other  than  the  right  one.  The  reason  for  this  is  evident 
from  the  following  consideration.  Assume  the  carriage  and  tool 
in  the  correct  position  and  the  nut  engaged,  the  lead  screw  having 
say  six  threads  per  inch ;  if  now  we  open  the  nut  and  move  the 
carriage  in  either  direction,  the  nut  cannot  catch  until  the  car- 


238 


MODERN    MACHINE    SHOP    TOOLS. 


riage  has  moved  a  distance  equal  to  the  pitch  of  the  lead  screw 
or  a  sixth  of  an  inch.  For  six  threads  this  of  course  catches 
the  next  thread;  for  twelve  threads  it  misses  one  and  catches 
the  second;  for  eighteen  it  misses  two  and  catches  the  third,  etc. 
For  threads  of  which  the  number  on  the  lead  screw  is  a  mul- 
tiple, as  i,  2  and  3  with  a  six-pitch  lead  screw,  the  nut  can  readily 
be  caught  by  inspection.  Thus,  if  cutting  one  thread  per  inch  the 
nut  will  catch  exactly  right  on  every  sixth  thread ;  in  cutting  two 
threads  it  catches  on  every  third  thread,  and  in  cutting  three  on 
every  second  thread.  Inspection  must  determine  whether  it  has 
caught  the  right  thread  before  setting  the  tool  into  the  cut. 
Other  threads,  as  8  or  10,  may  be  caught  by  inspection ;  thus  on 
the  six-thread  lead  screw>  moving  the  nut  three  threads  moves 


.  344. 


the  point  of  the  tool  y2  inch,  which  just  catches  the  fourth  thread 
on  the  eight-thread  work,  or  the  fifth  thread  on  the  ten-thread 
work.  For  any  pitch  other  than  those  for  which  the  above  is  ap- 
plicable set  the  tool  for  the  cut  slightly  beyond  the  end  of  the 
work  and  mark  the  position  of  the  carriage  in  any  convenient 
way.  A  stop  clamped  to  the  bed  against  which  the  carriage  may 
be  brought  is  very  convenient.  Next  mark  the  face-plate  and 
note  the  position  of  this  mark  with  reference  to  some  fixed  point 
on  the  lathe.  After  each  cut  open  the  nut,  move  the  carriage  to 
the  stop  and  bring  the  face-plate  to  the  mark,  when  the  nut  can 
be  engaged  with  the  lead  screw,  all  parts  being  in  the  same  posi- 
tion as  when  the  thread  was  started. 

It  is  frequently  desirable  to  run  a  rough  or  cored  hole  on  the 
dead  center.  This  would  quickly  cut  the  center  and  ruin  it  for 
accurate  work  until  reground.  The  hole  in  work  of  that  char- 


LATHE   WORK BETWEEN    CENTERS. 


239 


acter  is  usually  too  large  to  run  on  the  regular  center,  if  such 
were  desirable,  and  either  a  large  center  must  be  provided  to  carry 
it  or  the  hole  plugged  and  a  center  bearing  put  in  the  plug.  If 
the  hole  is  concentric  with  the  surface  to  be  machined  the  large 
center  is  the  cheapest  and  most  convenient  method.  It  is,  of 
course,  not  adapted  to  the  most  accurate  work,  but  for  ordinary 
operations  serves  its  purpose  well.  As  it  is  necessary  for  the 
center  to  revolve  with  the  work,  to  prevent  its  being  cut,  a  special 
device  is  required.  In  Fig.  344  is  shown  such  a  center,  common- 
ly known  as  a  pipe  center.  The  construction  is  evident ;  the  cone 
revolves  on  a  stud  and  backs  against  a  collar  having  a  simple  bear- 
ing surface  to  take  the  thrust.  It  is  also  provided  with  suitable 
channels  for  its  proper  lubrication. 

In  Fig.  345  is  shown  an  attachment  secured  to  the  carriage 


FIG.  345. 

of  an  engine  lathe  for  turning  shafting.  With  this  device  the 
shaft  is  roughed  down  by  two  tools  set  opposite  to  each  other, 
which  serves  to  balance  the  pressure  of  the  cut  and  reduce  the 
spring  to  a  minimum.  After  the  roughing  cuts,  it  passes  through 
a  suitable  bushing  held  in  the  head  and  receives  the  final  sizing 
and  finishing  cut  from  the  tool  shown  at  the  back  of  the  attach- 
ment. The  device  is  simply  a  follow  rest  carrying  three  tools 
instead  of  one. 

In  Fig.  346  is  shown  a  device  used  on  the  iathe  for  the  turn- 
ing of  cross-head  pins  or  other  surfaces  the  nature  of  which  pre- 
vents the  possibility  of  complete  rotation  of  the  work.  In  this 


240 


MODERN    MACHINE    SHOP    TOOLS. 


device  a  sleeve  carrying  two  gears  is  secured  on  the  nose  of  the 
lathe  spindle.  The  gear  next  to  the  spindle  bearing  is  keyed 
to  the  sleeve  and  rotates  with  the  spindle.  The  second  gear 
which  carries  the  work  driver  rotates  freely  upon  the  sleeve. 
The  first  gear  meshes  with  a  larger  one  that  is  carried  on  a 
bracket  secured  to  the  back  of  the  head  stock.  A  wrist  pin  in 
the  face  of  the  large  gear  drives  the  rack  which,  as  shown,  gears 
with  and  drives  the  loose  gear  and  thus  causes  the  work  to  rotate 
independent  of  the  spindle  rotation.  By  properly  proportioning 
the  diameter  of  the  gears  and  the  stroke  of  the  rack,  the  work 
can  be  made  to  oscillate  back  and  forward  through  any  desired 
part  of  the  revolution,  while  the  spindle  has  continuous  forward 


FIG.  346. 

rotation.  Thus  in  the  turning  of  the  cross-head  pin  shown,  the 
cross-head  moves  through  rather  more  than  one-half  of  the  full 
revolution,  thus  enabling  the  turning  of  a  little  more  than  one- 
half  of  the  pin.  The  cross-head  is  then  changed  end  for  end 
on  the  centers  and  the  other  half  turned.  Frequently,  with  cross- 
heads  to* be  used  in  single  acting  engines,  where  the  pressure  and 
wear  are  always  on  one  side  of  the  pin,  a  large  flat  can  be  ma- 
chined on  the  non-bearing  side  of  the  pin  and  sufficient  rotation 
obtained  to  completely  finish  the  pin  without  changing  ends 
with  the  work.  It  is,  of  course,  possible  to  turn  a  pin  of  this 
character  without  any  special  attachment,  by  either  pulling  the 
belt  backward  and  forward  and  driving  the  work  in  the  ordinary 


LATHE    WORK BETWEEN    CENTERS. 


24I 


manner  or  by  allowing  it  to  rotate  free  of  the  centers  and  oscil- 
lating it  by  means  of  a  wrench  or  lever.  These  latter  methods 
are  slow  and  require  an  extra  workman. 

An  ingenious  lathe  attachment  for  backing  off  the  teeth  of 
milling  cutters  is  shown  in  Fig.  347.  In  a  device  of  this  character 
either  the  tool  or  the  work  must  be  given  a  slight  in-and-out  mo- 
tion for  each  tooth  on  the  cutter  being  relieved.  In  the  case 
shown,  the  tool  is  held  in  the  tool  post  and  advanced  to  its  cut  in 
the  ordinary  manner.  The  mandrel  A  of  the  attachment  has  its 
centers  slightly  eccentric,  the  amount  of  the  eccentricity  being 


-FIG.  347. 

enough  to  produce  the  desired  amount  of  relief  on  one  tooth 
of  the  cutter  if  mounted  directly  on  the  mandrel.  The  arm  L 
is  secured  to  the  mandrel  and  driven  from  the  face-plate  by  the 
carrier  D.  The  sleeve  B,  which  carries  the  cutter  being  operated 
upon,  revolves  freely  upon  the  mandrel.  The  gear  b  is  secured 
to  the  sleeve  and  the  gear  a  is  loose  on  the  sleeve,  and  is  held 
from  rotating  by  the  arm  d  which  is  secured  to  it  and  rests  upon 
the  top  of  the  tool ;  c  is  a  pinion  carried  loose  on  the  stud  D  and 
gears  with  a  and  b.  Gear  b  has  a  smaller  number  of  teeth  than 
a,  and  as  a  does  not  rotate,  the  rotation  of  the  pinion  c  around  a 
advances  b  and  the  sleeve  and  cutter  a  certain  fixed  amount  at 


242  MODERN    MACHINE   SHOP    TOOLS. 

each  revolution  of  the  mandrel.  The  geared  ratio  is  such  for 
any  given  number  of  teeth  in  the  cutter  that  the  advance  per 
revolution  is  exactly  equal  to  the  circular  pitch  of  the  teeth  in 
the  cutter.  The  turning  is  such  as  to  bring  a  tooth  to  the  tool 
when  the  center  of  the  mandrel  is  farthest  from  the  tool,  thus 
giving  the  relief  as  the  tooth  advances  to  the  tool.  It  is  evident 
from  the  above  that  the  space  between  the  teeth  must  be  at  least 
equal  to  the  length  of  the  tooth.  As  this  division  of  space  and 
tooth  in  relieved  milling  cutters  is  not  usual,  it  is  necessary  to 
allow  the  cutter  blank  to  stand  still  while  the  mandrel  is  moving 
through  a  part  of  its  revolution.  This  is  accomplished  by  making 
the  circular  pitch  of  the  teeth  on  about  one-half  the  circumference 
of  b  equal  to  that  of  the  teeth  on  a  and  the  teeth  on  the  balance 
of  b  of  somewhat  greater  circular  pitch.  For  that  portion  where 
the  teeth  are  the  same  on  a  and  b,  the  pinion  simply  turns  around 
both  and  the  sleeve  remains  stationary.  During  the  balance  of 
the  revolution,  however,  the  sleeve  will  advance  an  amount  equal 
to  the  circular  pitch  of  the  cutter's  tooth. 

With  the  regular  tools  and  feeds  on  the  engine  lathe,  plane, 
cylindrical  and  conical  surfaces  are  readily  machined.  If  the  sur- 
face is  spherical  or  of  irregular  outline,  a  forming  tool  or  some 
special  attachment  must  be  used  on  the  lathe  to  produce  the  re- 
quired outline.  If  the  work  is  of  circular  section,  the  forming 
tool  can  usually  be  used  to  excellent  advantage,  as  illustrated  in 
Fig.  348.  In  this  case  the  tail-stock  cap  shown  in  the  figure  is 
first  chucked,  bored  at  A,  faced  at  B  and  threaded  at  D.  It  is 
then  placed  on  a  threaded  mandrel  and  driven  on  the  centers. 
The  forming  tool  E,  which  is  secured  in  the  ordinary  tool-post, 
forms  the  bead  and  is  set  in  until  the  proper  diameter  at  F  is  ob- 
tained. The  tool  G,  held  in  like  manner,  forms  the  hub  and 
rounded  end  of  the  cap,  the  tool  being  set  in  until  the  diameter 
at  H  is  equal  to  that  at  F.  A  common  tool  is  then  used  to  pro- 
duce the  cylindrical  surface  I.  If  the  length  I  is  short  it  would 
be  possible  to  combine  the  two  forming  tools  into  one.  As  the 
cutting  edge  is  a  long  one  it  is,  in  any  event,  desirable  to  rough 
off  the  scale  and  true  up  the  casting  before  applying  the  forming 
tools.  This  can  be  done  by  operating  the  regular  feeds  by  hand. 
If  the  work  does  not  run  true  when  the  forming  tool  is  set  to  the 
cut,  it  will  be  difficult  to  produce  satisfactory  results,  as  the 
spring  of  tool  and  work  will  vary  at  different  points  in  the  revo- 
lution. The  length  of  cutting  edge  that  can  be  employed  de- 


LATHE   WORK BETWEEN    CENTERS. 


243 


pends  in  any  case  upon  the  stiffness  of  the  work  and  the  rigidity 
of  the  lathe  -in  which  the  work  is  to  be  done.  Another  illustra- 
tion of  this  system  of  forming  is  shown  in  Fig.  349.  Here  the 
rim  of  a  hand  wheel  rounded  by  the  forming  tool  is  shown.  If 
the  section  of  the  rim  is  a  full  circle,  as  at  A,  two  settings  of 
the  tool  are  required,  one  of  which  is  illustrated  in  the  figure.  It 
is  here  even  more  important  than  in  the  example  shown  in  Fig. 
348  to  first  rough  the  stock  until  it  runs  true,  as  -the  heavy  cut  of 
the  forming  tool  will  otherwise  spring  the  work  so  that  it  will 
not  run  true  when  finished.  For  roughing  out  the  rim  a  side- 
cutting  tool  can  be  used  to  good  advantage,  setting  it  at  different 
angles  to  produce  a  section  similar  to  that  shown  in  the  figure  at 
B.  If  the  tools  are  carefully  made  and  kept  in  good  condition, 


J 

I.I 

FIG.  348. 


FIG.  349- 


very  satisfactory  results  can  be  obtained  upon  a  wide  range  of 
work,  similar  to  the  above  examples. 

The  tools  should  be  so  made  that  they  can  be  sharpened  by 
grinding  from  the  top  surface.  If  the  tool  is  carefully  made 
and  the  scale  removed  from  the  stock,  it  will  do  a  larger  amount 
of  work  before  dulling  materially.  Forming  tools  of  this  char- 
acter are  not  expensive  to  make,  and,  when  any  considerable 
amount  of  similar  work  is  to  be  produced,  will  pay  for  themselves 
very  quickly.  . 

The  tool  shown  in  Fig.  349  may  be  used  for  turning  balls  from 
stock  held  between  centers  or  in  a  chuck,  as  shown  in  Fig.  350. 


244 


MODERN    MACHINE   SHOP    TOOLS. 


If  the  stock  is  held  in  the  chuck,  the  ball  will  not  be  disfigured 
with  the  center  bearing.  A  small  tip  will,  however,  remain  where 
cut  from  the  body  of  the  stock.  In  forming  balls  in  this  manner 
it  is  necessary  to  caliper  the  diameter  carefully,  advancing  the 
tool  only  far  enough  to  produce  a  true  sphere.  This  method 
will  be  found  very  convenient  in  the  forming  of  balls  on  the  ends 
of  handles,  the  ball  in  such  cases  not  being  cut  from  the  body  of 
the  stock,  and  perfect  spheres  not  being  necessary.  In  Fig.  351 
is  shown  a  simple  ball-turning  device.  The  shank  of  the  cutter 
holder  is  round  and  fits  in  a  suitable  bearing  which  is  clamped 
to  the  tool  block.  On  the  outer  end  of  the  shank  is  secured  a 
long  lever  or  preferably  a  worm  and  gear  mechanism  for  rotating 


FIG.  350. 


FIG.  351. 


the  cutter  head  and  tool  to  the  work.  Although  a  truer  sphere 
can  be  obtained  with  this  device  than  by  the  use  of  the  forming 
cutter  shown  in  Fig.  350,  the  surface  will  not  be  as  smooth  as 
with  the  latter.  The  more  elaborate  device  shown  in  Fig.  352  is 
better  adapted  to  the  turning  of  larger  balls  than  either  of  the 
methods  above  referred  to.  While  this  attachment  can  be  pro- 
vided with  a  shank  and  held  in  the  tool-post,  it  is  much  more 
rigid  when  secured  directly  to  the  tool-block  or  in  the  place  of 
the  compound  rest.  The  construction  of  the  device  is  clearly 
shown  in  the  figure.  In  order  to  produce  a  true  sphere  the  cen- 
ter of  rotation  of  the  cutter-carrying  disk  must  be  exactly  under 
the  center  of  rotation  of  the  work,  and  the  distance  of  the  point 
of  the  tool  from  the  center  of  rotation  then  determines  the  radius 
of  the  ball.  By  setting  the  tool  with  its  point  past  the  center  of 


LATHE  WORK — BETWEEN    CENTERS. 


245 


the  disk  and  bringing  the  center  of  the  disk  back  from  the  center 
of  rotation  of  the  work  a  concave  section  can  be  produced  in  the 
work,  the  character  of  the  section  depending  upon  the  relative 
position  of  centers  and  tool  point.  With  work  held  in  the  chuck 
and  the  center  of  the  disk  under  the  center  of  rotation  of  the 
work,  it  is  possible  to  produce  on  the  end  of  the  work  either  a 
convex  or  concave  surface  depending  on  whether  the  point  of 
the  tool  is  back  or  ahead  of  the  center  of  rotation  of  the  disk. 

A  convex  or  concave  surface  can  readily  be  turned  with  a  tool 
held  in  the  common  compound  rest,  the  only  difficulty  being  in 
the  control  of  the  feed.  When  the  cuts  are  light,  however,  satis- 


FIG.  352. 


FIG.  353- 


factory  results  can  be  obtained  by  moving  the  rest  by  hand,  hav- 
ing its  clamp  bolts  tightened  just  enough  to  steady  the  motion. 

In  cases  where  the  outline  is  irregular  and  too  long  to  be 
conveniently  produced  with  the  forming  tool,  a  common  tool 
may  be  made  to  do  the  work,  its  motion  being  controlled  by  a 
guide  having  the  same  outline  as  the  one  desired  and  controlling 
the  tool  on  the  taper-attachment  principle.  The  general  arrange- 
ment is  shown  in  the  top  view  of  a  lathe  carriage,  Fig.  353.  In 
this  case  the  slide  is  disconnected  from  the  cross-screw.  B  B  is 
the  guide  which  is  secured  to  the  bed  of  the  lathe  and  independ- 
ent from  the  carriage.  The  finger  A  is  secured  to  the  slide  and 
bears  against  the  guide  B  B.  A  cord  C  is  attached  to  the  slide, 


246 


MODERN    MACHINE    SHOP   TOOLS. 


passes  over  the  pulley  D  and  carries  the  weight  W  which  serves 
to  hold  the  finger  A  to  the  guide  at  all  times.  The  point  of 
the  cutting  tool  must  jtravel  with  the  finger  A,  and,  tracing  the 
outline  of  B  B,  produce  the  same  outline. on  the  work.  In  this 
arrangement  the  tool  is  usually  set  to  the  work  by  adjusting  it 
through  the  tool-post.  A  threaded  adjustment  in  the  finger  A 
makes  a  good  adjustment  for  the  finer  tool  settings.  This  method 
is  applicable  only  when  the  cross-section  of  the  work  is  round. 
If  an  irregular  cross-section  is  required,  a  different  arrangement 
involving  the  use  of  a  pattern  or  dummy  is  generally  employed. 
The  dummy  is  a  pattern  of  the  same  cross-section  as  that  re- 
quired on  the  work,  and  is  mounted  either  on  the  same  axis  as 
that  of  the  work  rotation,  or  on  a  separate  axis  so  geared  as  to 
make  the  same  number  of  revolutions  as  the  work,  When  the 


FIG.  354. 

work  is  short  and  both  it  and  the  pattern  can  be  mounted  on  the 
same  axis,  the  former  method  is,  owing  to  its  simplicity,  prefer- 
able. In  Fig.  354  is  illustrated  the  former  method.  As  in  Fig. 
353,  the  cross-feed  screw  is  disconnected  from  the  cross-slide  and 
a  weight  provided  for  holding  the  finger  against  the  pattern  B, 
which  rotates  with  the  work.  A  second  tool-post,  back  of  the 
one  carrying  the  finger,  holds  the  tool  that  operates  on  the  work. 
It  is  evident  that  the  motion  of  tool  point  and  finger  is  the  same 
and  that  the  outline  of  the  work  will  be  the  same  as  that  of  the 
pattern.  If  the  two  tool-posts  cannot  be  set  sufficiently  far  apart 
to  allow  for  the  required  length  of  cut,  the  finger  can  be  carried 
on  a  suitable  bracket  secured  to  the  side  of  the  tool-block.  It  is 
quite  possible  by  careful  adjustment  to  start  the  cut  with  the  use 


LATHE   WORK BETWEEN   CENTERS. 


247 


of  the  pattern,  and  allow  the  finger  to  lead  from  the  pattern  on  to 
the  work,  thus  enabling  a  long  cut  to  be  made  with  a  short  pat- 
tern. A  careful  readjustment  of  the  finger  is  required  for  each 
cut  in  this  case.  It  is  not  necessary  that  the  pattern  be  of  the 
same  size  as  the  work  section,  as  it  is  frequently  desirable  to 
make  it  of  a  different  size. 

It  is  quite  possible  to  adapt  the  method  of  Fig.  354  to  internal 
work.  In  Fig,  355  the  work  is  secured  on  the  tool-block  and  the 
pattern  on  the  boring  bar.  In  this  case  the  work  moves  with  the 
pattern  instead  of  the  tool.  The  example  shown  illustrates  the 


FIG.  355. 


FIG.  356. 


method  of  boring  an  elliptical  hole.  By  using  a  movable  head 
boring  bar  a  thin  pattern  is  all  that  is  required.  As  a  wide  range 
of  patterns  can  be  used  many  forms  of  cams  can  be  produced  by 
the  above  method. 

The  same  method  shown  in  Fig.  353  is  applicable  to  face 
work  on  stock  held  against  the  face-plate  or  in  the  chuck.  In 
this  case  the  weight  is  placed  at  the  end  of  the  bed,  the  guide  is 
secured  to  the  cross-slide  and  the  finger  to  the  tail-stock,  all  as 
shown  in  Fig.  356.  Many  outlines  can  readily  be  produced  in 
this  manner.  The  tool  is  operated  by  the  regular  cross-feed 
mechanism. 


CHAPTER  XVIII. 

LATHE    WORK    ON    FACE-PLATE,    CHUCK    AND    CARRIAGE. 

A  large  portion  of  the  work  done  in  the  lathe  may  be  classed 
as  boring  work  as  it  comes  under  the  following  classifications : 
center  rest,  carriage,  face  plate  and  chuck  work.  An  example 
of  a  boring  operation  under  the  first  class  was  shown  in  Fig. 
333.  As  work  of  this  kind  is  usually  performed  on  solid  stock, 
a  hole  must  first  be  drilled  sufficiently  large  to  allow  the  boring 
tool  to  enter.  The  drilling  of  this  hole  can  be  done  to  good 
advantage  in  the  lathe  by  using  a  twist  drill  held  on  the  tail 
center.  The  taper  shank  drill  with  holder,  shown  in  Fig.  357,  is 
best  suited  to  this  work  as  it  clears  itself  readily  of  the  cuttings 
and  the  holder  prevents  injury  to  the  shank.  In  no  case  should 
the  taper  shank  drill  be  held  by  a  dog  secured  on  the  shank,  as 
it  is  quite  certain  to  slip  and  injure  the  tool.  If  a  dog  is  to  be 
used  at  all  for  this  purpose,  it  should  be  in  connection  with  a 
straight  shank  drill  provided  with  a  flat  spot  on  the  shank  for  the 
set-screw  of  the  dog  to  seat  upon.  When  considerable  drilling 
of  this  kind  is  to  be  done  in  a  lathe,  it  is  advisable  to  have  a  set 
of  drill  sockets  fitted  to  the  bearing  in  the  tail  spindle.  This 
not  only  makes  a  more  satisfactory  method  for  holding  the  drill, 
but  overcomes  the  danger  of  the  drill  drawing  off  the  tail  center 
and  being  bent  or  broken  by  the  cramp  it  would  receive  due  to 
the  single-handled  holder. 

When  holes  of  a  considerable  depth  are  to  be  drilled  in  this 
manner  in  steel,  it  is  difficult  to  properly  lubricate  the  cutting 
edges  of  the  drill,  and  often  the  work  and  tool  begin  to  heat  and 
the  cuttings  to  fill  up  the  flutes.  The  drill  must,  therefore,  be  fre- 
quently removed  for  oil  and  cleaning.  These  difficulties  are  al- 
most wholly  overcome  by  using  the  oil  tube  drill  in  places  of 
this  kind,  as  it  provides  for  a  constant  and  liberal  supply  of  oil 
at  the  point,  which  not  only  improves  the  cutting  and  clear- 
ing of  the  chips,  but  carries  away  the  heat  of  friction  and  thus 
enables  the  crowding  of  the  drill  to  its  full  cutting  capacity.  As 
in  this  class  of  drilling  the  drill  does  not  rotate,  a  common  socket 
can  be  used  in  connection  with  the  oil  tube  drill,  it  being  simply 
necessary  to  tap  for  a  small  gas  pipe  connection  in  the  side 


LATHE  WORK  UN    FACE-PLATE,  ETC.  249 

of  the  socket  over  the  supply  hole  in  the  shank  of  the  drill.  In 
an  operation  of  this  kind  the  important  point  is  to  get  the  drill 
started  true.  If  the  work  has  been  centered  for  other  operations 
previous  to  the  drilling,  this  center  forms  a  seat  for  steadying 
the  point  of  the  drill  in  starting.  Even  though  this  center  runs 
perfectly  true,  it  cannot  be  relied  upon  for  starting  the  drill  true. 
It  is,  therefore,  necessary  to  steady  the  end  of  the  drill  in  a  dif- 
ferent manner.  In  Fig.  358  is  shown  a  common  method.  The 
steadying  tool,  which  is  held  in  the  tool  post,  is  made  to  bear 
against  the  front  side  of  the  drill,  as  close  to  the  point  as  pos- 
sible. The  drill  should  be  held  so  that  one  lip  is  on  the  back 
side  of  the  work  surface  or  opposite  the  steadying  tool.  As 
the  cut  is  started,  the  drill  is  crowded  slightly  back  of  the  center, 
making  the  one  lip  do  all  the  cutting.  This  makes  it  virtually  a 
rigid  boring  tool  that  cannot  sway  and  produces  a  surface  con- 
centric with  the  axis  of  rotation.  Just  before  the  drill  begins  to. 
cut  a  full  diameter  hole,  the  steady  tool  should  be  backed  away 
and  the  point  of  the  drill  left  free  to  follow  the  center  of  rotation. 
If  this  work  is  carefully  performed,  it  is  possible  to  start  a  drill 
almost  exactly  true.  When  the  surface  into  which  the  drill  is  to 
enter  is  plane,  the  centering  tool  with  flat  drill  point  shown  in 
Fig.  359,  and  held  in  the  tool  post,  is  used.  It  forms  a  good  seat 
for  the  drill  to  start  in. 

For  uniformly  true  and  central  holes  the  drill  cannot  be  relied 
upon,  and  its  use  in  the  lathe  is  confined  almost  entirely  to  the 
opening  up  of  the  work  previous  to  using  a  boring  tool.  For 
example,  if  a  i-inch  hole  is  required  in  a  piece  of  work  held  on  a 
face  plate  or  in  a  chuck,  a  i-inch  drill  could  not  be  depended  upon 
for  anything  like  a  satisfactory  result  and  a  63-64-inch  drill  fol- 
lowed by  a  i-inch  reamer  would  be  almost  as  bad.  The  only 
correct  way  in  such  a  case  would  be  to  first  use,  say,  a  15-1 6-inch 
drill  which  would  remove  most  of  the  stock  and  allow  a  boring 
tool  to  enter.  It  can  then  be  bored  with  the  boring  tool  to  the 
proper  diameter  or,  if  it  is  to  be  finished  with  a  reamer,  it  should 
be  bored  to  within  about  i-ioo  of  an  inch  of  the  exact  size,  which 
trues  the  hole  perfectly  previous  to  the  reaming.  The  reamer 
should  be  held  on  the  tail  center,  which  latter  must  be  exactly 
central.  If  the  tail  center  is  offset,  a  tapered  hole  will  necessarily 
result. 

The  size  of  drill  to  use  for  opening  up  previous  to  boring  de- 
pends upon  the  nature  of  the  work.  If  the  finished  hole  is  to 


250 


MODERN    MACHINE   SHOP   TOOLS. 


be  small  in  diameter  and  deep,  a  drill  as  large  as  possible  should 
be  used,  since  the  boring  tool  will  be  a  long  and  springy  one 
necessitating  light  cuts  which  will  remove  the  metal  more  slowly 
than  would  the  drill.  If,  on  the  other  hand,  the  hole  is  to  be 
of  large  diameter  and  not  deep,  a  drill  should  be  used  that  is  only 
large  enough  to  enable  a  short,  stiff  boring  tool  to  readily  enter, 
as  the  boring  tool  will  remove  the  stock  faster  than  the  drill 
would.  In  using  the  boring  tool,  it  is  generally  well  to  feed 
both  ways  through  the  work  as  this  tends  to  equalize  the  effect 
of  the  wear  on  the  cutting  edge.  In  cases  where  accurate  bores 
are  required,  it  is  quite  necessary  not  to  change  the  depth  of 
cut  after  the  cut  has  started,  as  the  effect  of  the  spring  of  the 
tool  will  be  quite  marked.  A  boring  tool  tends  to  make  the 
mouth  somewhat  larger  than  the  balance  of  the  hole  it  is  boring, 


359. 


fl 

If         o          ft 

°  to 

Fia.  36H. 

Fig.  '358. 


FIGS.  357  TO  360. 


because  the  tool  does  not  take  its  full  spring  until  the  cutting 
edge  passes  the  end  of  the  bore. 

In  the  boring  of  parallel  holes,  the  height  of  the  cutting  edge 
does  not  affect  the  parallelism  of  the  bore.  With  tapered  bores, 
however,  it  is  necessary  that  the  tool  set  at  the  height  of  'the 
center,  as  a  different  taper  than  the  one  required  will  result  if 
the  cutting  edge  is  above  or  below  the  center.  The  amount 
of  taper  in  either  case  would  be  somewhat  smaller  than  when 
the  cutting  edge  is  at  the  center.  When  the  bores  are  long  and 
of  large  diameter,  the  boring  tool  is  no  longer  well  suited  to  the 
work  and  what  is  known  as  a  boring  bar  is  used.  These  bars  are 
of  two  kinds,  those  having  a  cutting  tool  fixed  in  its  position  on 
the  bar,  and  those  in  which  a  cutting  tool  is  secured  in  a  mov- 
able head  which  traverses  over  the  bar.  The  former  are  the  least 


LATHE  WORK  ON  FACE-PLATE.  ETC. 


251 


desirable,  inasmuch  as  they  must  be  somewhat  more  than  twice 
the  length  of  the  bore,  while,  with  the  latter,  a  length  but  slightly 
greater  than  the  bore  is  all  that  is  required. 

In  Fig.  360  is  shown  a  plain  boring  bar  of  the  former  type. 
The  cutting  tool  may  be  of  flat  steel  secured  in  a  mortise  through 
the  bar  by  suitable  wedges,  or  it  may  be,  as  shown  in  the  figure, 
of  round  steel,  fitting  nicely  the  hole  through  the  bar  and  secured 
in  position  by  a  set-screw  which  seats  on  a  flat  spot  filed  on 


£ 


FIGS.  361  AND  362. 


the  tool.  The  set-screw  should  have  a  smooth,  flat  point  so  that, 
when  moderately  tightened,  the  tool  can  be  driven  under  it  in 
adjusting  the  cut.  This  class  of  boring  bar  is  suitable  only  on 
work  secured  to  the  carriage,  as  the  work  must  be  given  the  feed 
over  the  cutting  tool.  In  Fig.  361  is  shown  a  traverse  head 
boring  bar.  A  tool-carrying  head  fits  nicely  upon  this  bar.  It  is 
splined  to  receive  the  key  which  is  secured  in  the  head.  The 
feed  or  traverse  of  the  head  is  accomplished  by  means ^of  a  screw 
usually  driven  by  a  star  feed  from  one  end.  By  substituting  for 


252  MODERN    MACHINE    SHOP    TOOLS. 

the  star  a  spur  gear  on  the  screw  and  gearing  this  with  a  pinion, 
keyed  on  the  lathe  center,  a  smooth,  steady  screw  feed  results. 

When  the  bar  is  of  large  diameter  as  compared  with  the  head, 
the  screw  can  be  dropped  into  a  suitable  spline,  thus  getting  it  out 
of  the  way  and  protecting  it  from  injury.  Boring  bars  of  modr 
erate  size  are  preferably  made  of  a  medium  grade  of  tool  steel, 
as  this  is  much  stiffer  than  mild  steel.  For  large  bars,  mild  steel 
or  cast  iron  is  suitable.  When  cast  iron  is  used,  the  ends  should 
be  plugged  with  steel  to  receive  the  centers,  as  the  cast  iron  wears 
too  rapidly  to  retain  an  accurate  center  bearing.  Movable  head 
boring  bars,  in  which  the  head  is  traversed  by  means  of  the  regu- 
lar carriage  feed,  can  be  used  to  good  advantage  in  cases  where 
the  bar  remains  stationary  and  the  work  rotates.  In  Fig.  362  is 
shown  a  movable  head  bar  of  this  class  operating  upon  a  cylinder 
secured  to  the  face  plate.  The  bar  carries  a  long  sleeve,  one 
end  of  which  terminates  in  the  cutter.  A  dog  or  wrench  secured 
to  the  outer  end  of  the  sleeve  prevents  it  from  turning  and  the 
tool  post  bearing  against  the  arm  of  the  dog  transmits  the  regu- 
lar carriage  feed  to  the  tool.  By  off-setting  the  tail  center  as 
shown  by  the  dotted  line,  a  tapered  hole  results  which  will  be 
larger  at  the  inner  end  of  the  bore,  with  the  tool  set  as  in  the 
figure,  but  if  the  cutting  tool  is  set  at  180  degrees  from  the  posi- 
tion shown,  the  bore  will  be  larger  at  the  outer  end,  as  indicated 
by  the  dotted  lines. 

Unless  the  character  of  the  work  is  such  as  to  enable  its  outer 
end  to  be  run  in  the  center  rest  when  the  bore  is  long,  rotating 
the  work  is  not  satis  faqtory,  as  its  outer  end  is  too  far  from  the 
lathe  spindle  to  be  sufficiently  rigid.  When  the  work  is  clamped 
to  the  carriage,  it  is  always  preferable  to  feed  the  cutting  tool 
rather  than  the  work  as  the  carriage  can  then  be  clamped  rigidly 
to  the  bed.  This  insures  a  more  accurate  bore  as  the  carriage, 
unless  very  closely  gibbed,  will  lift  on  the  up  cut  of  the  tool. 

In  Fig.  363  is  shown  a  movable  head  bar  operating  upon  a 
cylinder  clamped  to  the  lathe  carriage.  In  this  case,  off-setting 
the  tail  center  as  the  bar  rotates  will  not  enable  the  boring  of  a 
tapered  hole.  The  tapered  hole,  however,  can  be  obtained  by  off- 
setting one  end  of  the  boring  bar  as  shown  dotted  in  the  figure. 
If  desired,  the  offset  can  be  put  on  the  bar  itself,  in  which  case  it 
can,  as  shown  in  Fig.  364,  be  offset  at  the  tail  center  end.  By 
making  the  center  bearing  adjustable,  as  shown  in  the  figure,  any 
desired  taper  within  the  limits  of  its  adjustment  may  be  obtained. 


LATHE   WORK  ON   FACE-PLATE,   ETC. 


253 


In  boring  work,  it  is  very  important  to  see  that  the  work  is  prop- 
erly secured  on  the  carriage,  face  plate  or  in  the  chuck.  It 
must  be  held  sufficiently  rigid  to  prevent  its  working  loose  and, 
at  the  same  time,  must  not  be  sprung  out  of  shape  as,  in  such 
cases,  when  finished  and  removed  from  the  lathe,  it  will  be  found 
out  of  true.  In  straight  cylinder  boring,  more  than  one  cutting 


FIGS.  363  AXD  364. 


tool  is  usually  employed  as  a  single  cutter  Springs  the  bar,  thus 
cequiring  very  light  finishing  cuts  to  produce  satisfactory  results. 
Three  cutters  steady  the  bar  nicely,  especially  if  care  is  exer- 
cised in  setting  the  cuts  about  equal.  A  tool  for  finishing  should 
not  follow  a  roughing  cutter,  inasmuch  as  all  the  springing  of  the 
roughing  cutter,  due  to  its  unequal  work  at  different  points  of 
the  bore,  will  be  transmitted  directly  to  the  finishing  cutter  and 


254  MODERN    MACHINE   SHOP    TOOLS. 

thus  produce  an  untrue  cylinder.  To  insure  true  work,  the  fin- 
ishing cuts  should  always  be  light  ones. 

The  chucking  of  most  work  requires  thought  and  judgment. 
Fixed  rules  cannot  be  laid  down,  as  each  case  must  be  considered 
from  its  own  peculiarities.  The  surface  to  be  machined,  the 
character  of  the  finish,  the  possible  chances  for  gripping  it  in  the 
chuck  jaws,  and  the  likelihood  of  the  work's  springing  are  all 
questions  that  arise  with  each  case. 

Frequently  the  form  of  the  work  is  such  that  it  cannot  be 
held  ia  the  chuck.  In  such  cases  it  is  usually  possible  to  clamp 


FIG.  365. 

the  work  to  the  face-plate  or  to  an  angle-plate  secured  on  the 
face-plate.  Setting  up  work  in  this  manner  requires  care  and 
time.  If  there  are  many  similar  pieces  to  be  operated  upon,  it 
usually  pays  to  get  up  a  special  chuck  for  holding  them.  Take 
for  example  the  cylinder  head  shown  in  Fig.  365.  This  head  must 
be  bored  on  the  inside  and  faced  on  the  bottom.  The  post  on 
the  top  of  the  head  is  so  high  that  the  regular  chuck  jaws  will  not 
reach  the  body  of  the  casting.  If  but  a  single  head  was  to  bo 
finished,  it  would  be  secured  to  a  knee-plate  on  the  face-plate,  as 
shown  in  Fig.  366.  As  large  numbers  are  to  be  machined,  how- 
ever, the  special  chuck  shown  in  Fig.  365  is  employed.  In  a  case 


LATHE   WORK  ON   FACE-PLATE,   ETC. 


255 


of  this  kind  a  set  of  special  jaws  could  be  used  in  the  standard 
chuck.  They  would  not  be  as  convenient,  however,  as  the  special 
chuck. 

It  is  usually  best  to  chuck  work  from  the  outside  rather  than 
from  the  inside,  as  the  danger  of  breaking  is  less.  When  the 
work  is  light,  and  it  must  for  the  roughing  cuts  be  chucked 
firmly,  it  is  certain  to  be  somewhat  distorted.  In  such  cases  the 
chuck  jaws  should  be  eased  off  slightly  before  taking  the  finishing- 
cut.  Small  pulleys,  gear  blanks,  etc.,  should  when  possible  bo 


FIG.  366. 


chucked  on  the  hub.  When  so  held  and  properly  bored  and 
turned,  the  finished  work  will  run  true.  If  the  rim  of  the  blank 
or  pulley  is  heavy,  as  is  the  case  with  balance  wheels,  it  should  be 
chucked  out  upon  the  inside  of  the  rim,  setting  the  chuck  jaws 
as  close  to  the  ends  of  the  arms  as  possible.  This  allows  the 
tool  to  be  brought  to  operate  upon  the  entire  rim  surface  as  well 
as  upon  the  bore.  Upon  pulleys  having  light  rims,  and  too  large 
iti  diameter  to  chuck  by  the  hub,  carriers,  as  shown  in  Fig.  367, 
secured  to  the  face-plate  and  clamped  on  the  pulley  arms  near 
the  rim,  form  excellent  drivers. 


256 


MODERN    MACHINE    SHOP    TOOLS. 


When  the  work  has  a  reamed  bore  upon  which  it  can  be 
finished,  a  split  chuck  can  be  used  to  excellent  advantage.  Such 
a  chuck  for  smaller  diameters  is  shown  in  Fig.  368.  The  taper 
shank  fits  the  center  bearing  in  the  head  spindle.  The  nose  is 
drilled,  tapped  and  split,  as  shown.  A  tapering  screw  fits  the 
threaded  bore,  and  when  screwed  in,  expands  the  chuck  enough 


PIG.  367. 

to  grip  in  a  close-fitting  bore.  These  chucks  should  be  tempered 
and  ground  perfectly  true.  Their  advantage  over  a  hardened 
mandrel  on  this  class  of  work  lies  largely  in  the  convenience  in 
putting  on  and  removing  the  work  and  in  the  ease  with  which 
the  cutting  tool  may  be  brought  to  the  edge  of  the  bore  without 
fear  of  running  into  the  mandrel. 

Nearly  all  turret  machine  operations  are  upon  chucked  work. 


FIG.  368. 

In  the  case  of  work  upon  bar  stock  some  form  of  universal  chuck 
is  always  used.  The  stock  is  of  comparatively  small  diameter 
and  the  tools  that  operate  upon  it  are  brought  successively  into 
action,  either  by  hand  or  automatically.  A  pointing  box  tool  bevels 
the  end ;  a  roughing  box  tool  passes  over,  taking  the  bulk  of  the 
stock ;  the  finishing  box  tool  reduces  to  exact  diameter ;  the  die 


LATHE  WORK  ON   FACE-PLATE,   ETC. 


257 


threads  it,  and  the  cut  of  slide  with  an  inverted  tool  in  the  back 
holder  chamfers  the  head,  after  which  the  tool  in  the  front  head 
cuts  it  off.  For  this  class  of  work  on  steel  a  copious  supply  of 
thread-cutting  oil  must  be  constantly  applied  to  the  tool. 

For  bar  work  a  comparatively  small  assortment  of  tools  may 
be  made  to  do  a  very  wide  range  of  work,  but  with  turret  ma- 
chines operating  upon  cast  work,  this  is  not  usually  the  case,  as 
each  particular  job  usually  requires  its  own  special  tools.  Boring 
in  the  turret  lathe  is  usually  performed  with  a  bar  having  a  pilot 
point  and  carrying  suitable  cutters,  as  shown  in  Fig.  369. 

A  suitable  bushing  in  the  nose  of  the  spindle  steadies  the  pilot 
end  of  the  bar.  A  roughing  cutter  is  used  to  remove  the  heavy 
stock,  and  this  is  followed  by  a  sizing  cutter  in  a  second  bar,  or  if 
the  distance  from  the  inner  end  of  the  bore  to  the  nose  of  the 


FIG.  369. 

spindle  is  sufficient,  a  sizing  cutter  may  be  used  in  the  first  bar. 
It  should  be  so  located  that  it  does  not  start  its  cut  until  after 
the  roughing  cutter  clears  the  work,  as  otherwise  the  spring  of 
the  roughing  cut  will  affect  the  truth  of  the  finishing  cut.  It  is 
usual  to  finish  the  hole  to  exact  size  with  a  reamer,  carried  also 
in  the  turret. 

The  above  is  a  job  for  a  plain  turret  lathe.  If  face  surfaces 
are  to  be  machined,  and  the  number  of  pieces  required  will  war- 
rant making  the  tools,  a  facing  cutter  may  be  used  as  shown  in 
Fig.  370.  The  hole  having  been  reamed  to  size  in  the  work,  the 
pilot  bar  P  steadies  the  work  while  it  is  operated  upon  by  the 
face  cutter  C,  which  is  secured  in  a  heavy  cast  head  H,  which  in 
turn  is  bolted  to  one  of  the  flat  faces  of  the  hexagon  turret. 
Heavy  spindle  power  is  required  to  drive  cuts  of  this  character. 


258 


MODERN    MACHINE   SHOP   TOOLS. 


When  the  cuts  are  long  it  is  advisable  to  use  two  cutters,  the  first 
with  serrated  cutting  edge  to  break  up  the  scale  before  putting 
the  finishing  cutter  into  the  work.  The  pilot  bars  should  be  hard- 


FIG  370. 


ened  and  ground  to  correct  size,  as  there  is  danger  with  soft  bars 
of  their  seizing  the  surface  of  the  bore. 

With  the  turret  lathes,  Figs.  263  and  269,  where  an  indepen- 
dent carriage  is  provided,  operations  on  the  face  and  circumference 


FIG.  371. 

of  the  work  can  be  carried  on  at  the  same  time  the  turret  tools 
are  operating  on  the  bore.  In  Fig.  371  is  shown  a  Gisholt  lathe 
operating  upon  a  stepped  pulley.  The  bore  having  been  finished, 
the  long  pilot  bar  is  passed  through  it  and  entered  into  the  bush- 


LATHE   WORK  ON   FACE-PLATE,   ETC. 


259 


ing  in  the  nose  of  the  spindle,  thus  forming  a  substantial  support 
for  the  work.  The  heavy  cast  head  secured  to  the  carriage  is 
provided  with  a  cutting  tool  for  each  step  of  the  cone,  thus  finish- 
ing all  the  steps  in  the  time  of  the  feed  across  one. 

In  Fig.  372  is  shown  a  method  of  finishing  cones  and  similar 
work  in  heavy  plain  turret  lathes.  The  yoke  YY  is  bolted  to  a  flat 
on  the  turret.  A  stationary  mandrel  XX  carries  the  work.  A 
short  hollow  mandrel  W  is  secured  to  the  face-plate,  exactly  true 
with  the  spindle,  and  having  a  neat  bearing  in  the  yoke  YY.  XX 
fits  the  hole. in  W,  and  a  suitable  driver  on  the  end  of  W  engages 
the  arms  of  the  work,  causing  it  to  rotate  upon  a  stationary 
spindle. 

Feeding  the  turret  forward  advances  the  cutters  across  the 


FIG.  372. 

steps  of  the  cone.     These  methods  are,  of  course,  applicable  to 
a  very  wide  range  of  work. 

If  it  is  required  to  bore  a  hole  in  a  piece  of  work  parallel  to 
another  hole  that  has  been  bored  in  the  lathe,  it  is  necessary  to 
offset  the  work  until  the  required  bore  is  concentric  with  the  axis 
of  rotation.  This  involves  very  accurate  chucking,  and  if  the 
work  is  large,  the  swing  of  the  lathe  will  frequently  not  permit 
sufficient  offset.  When  enough  work  of  this  character  is  to  be 
done  to  warrant  its  construction  the  attachment  shown  in  Fig.  373 
will  be  found  very  satisfactory.  Its  construction  is -simple,  con- 
sisting of  a  suitable  bearing  that  can  be  secured  to  the  tool' block 
and  carrying  a  spindle  or  boring  bar.  A  pulley  for  driving  the 
bar  can  be  attached  directly  to  its  outer  end,  or  if  the  amount  of 
use  the  attachment  is  to  be  put  to  will  warrant  it,  it  can  be  con- 
structed as  shown  in  the  figure.  The  spindle  in  this  case  is  pro- 
vided with  a  taper  bearing  at  F  to  receive  a  taper  shank  drill,  an 


260 


MODERN    MACHINE    SHOP    TOOLS. 


end  milling  cutter  or  a  short  boring  bar.  The  outer  end  of  the 
spindle  carries  the  gear  B ;  gear  C  meshes  with  B  and  is  carried 
on  a  radially  adjustable  stud.  Gears  B  and  C  should  be  made 
to  interchange  or  even  be  replaced  by  others,  and  thus  provide 
for  changes  of  speed  on  the  spindle.  The  driving  pulley  E  is 
carried  loose  on  a  suitable  stud  D,  which  clamps  over  the  nose  of 
the  tail  spindle.  A  pair  of  universal  couplings  with  a  telescop- 
ing shaft  connects  E  and  C  and  transmits  the  power.  In  the 
operation  of  this  attachment  belted  power  is  transmitted  to  E 
and  to  the  regular  lathe  feeds  used  for  advancing  the  cutter  to 
the  work.  The  face  plate  must  be  blocked  to  prevent  the  work 
from  turning.  In  Fig.  374  is  shown  a  satisfactory  method  of 
blocking  the  face  plate  and,  at  the  same  time,  of  providing  an 
adjustment  for  accurately  locating  the  position  of  the  bore.  An 
attachment  of  this  kind  will  frequently  be  found  quite  valuable 


.  373- 


FIG.  374. 


as,  for  example,  in  the  boring  of  a  crank  disc  for  shaft  and 
crank  pin,  the  attachment  boring  the  hole  for  the  pin  with  rea- 
sonable certainty  of  getting  it  parallel  with  the  bore  for  the  crank 
shaft. 

Fig.  375  serves  to  illustrate  a  class  of  attachments  that  can  be 
advantageously  used  for  performing  milling  operations  on  the 
lathe.  The  attachment  shown  is  secured  to  the  tool  block  in  the 
place  of  the  tool  post.  The  construction  is  such  as  to  provide 
for  suitable  vertical  adjustment,  and  the  milling  cutter  to  be  used 
h  carried  on  an  arbor  held  between  the  lathe  centers.  The  attach- 
ment shown  is  suitable  only  for  light  milling  operations,  as  it  is 
not  sufficiently  rigid  for  heavy  work.  An  attachment  constructed 
along  the  same  lines  and  attached  to  the  carriage  in  place  of  the 
cross-slide  can  be  made  sufficiently  rigid  to  enable  heavy  work 


LATHE   WORK  OX    FACE-PLATE,   ETC. 


26l 


to  be  done  upon  it  and  will,  in  the  absence  of  a  milling  machine,  be 
found  a  most  useful  device. 

The  boring  of  spherical  sockets  can  readily  be  accomplished 
by  means  of  the  special  attachment  shown  in  Fig.  376.  The 
small  gear  is  mounted  on  the  flattened  end  of  a  stub  center  which 


FIG.  375. 


C 


FIG.  376. 

is  fitted  to  the  tail  spindle  bearing.  The  cutting  tool  is  secured 
in  the  face  of  this  gear  and  the  gear  caused  to  rotate  by  means 
of  the  rack  which  is  carried  in  the  tool-post  and  actuated  by  the 
regular  cross-feed  on  the  lathe.  The  cutting  edge  of  the  tool 
must  be  set  at  the  height  of  the  center. 


262  MODERN    MACHINE    SHOP    TOOLS. 

When  a  piece  of  work  is  to  be  externally  turned  to  fit  a  certain 
hole  or  bore  the  character  of  the  fit  must  be  specified  as  a  working 
fit,  which  may  be  close  or  easy ;  a  driving  or  forced,  or  a  shrink 
fit.  The  working  fit  indicates  that  the  one  moves  over  the  other, 
either  by  sliding  or  by  rotation,  and  the  niceness  of  the  fit  will 
depend  on  the  accuracy  required  and  the  means  of  producing 
perfectly  cylindrical  surfaces.  In  all  working  fits  the  difference 
in  diameter  of  cylindrical  surfaces  must  be  enough  to  allow  a  thin 
film  of  oil  to  cover  the  surfaces.  When  very  accurately  formed 
the  difference  in  diameter  can  be  extremely  small  and  a  perfect 
working  fit  maintained.  If,  however,  the  surfaces  are  not  per- 
fectly true  and  smooth  more  allowance  must  be  made,  as  other- 
wise the  motion  of  the  one  upon  the  other  produces  heat,  which 
usually  causes  unequal  expansion  and  consequent  locking  of  the 
two  parts,  the  lubricant  being  forced  from  the  surface.  If  slid- 
ing or  rotation  is  forced  under  these  conditions,  the  surfaces  will 
seize  and  abrasion  occurs. 

The  larger  the  diameter  the  more  allowance  must  be  made 
for  proper  working  fits.  For  small  spindles  accurately  surfaced 
.00025  to  .001  inch  is  sufficient,  while  with  larger  sizes  from  .005 
to  .01  inch  must  be  given. 

Driving  and  press  fits  are  those  in  which  the  shaft  or  plug 
is  finished  slightly  larger  than  the  bore  and  forced  into  the  bore 
by  driving  or  by  pressure.  On  small  work  the  operator  usually 
depends  upon  his  judgment  as  to  the  proper  allowance.  A  differ- 
ence for  each  inch  of  diameter  of  the  work  of  from  .001  to  .003 
usually  covers  the  range  from  medium  to  heavy  forced  fits. 
Shrink  fits  may  be  conveniently  made  on  work  of  small  or  large 
diameter,  as  they  involve  only  a  means  for  heating  up  the  ring 
or  bore  an  amount  sufficient  to  enlarge  it,  by  expansion,  enough 
to  allow  the  shaft  or  center  to  enter  easily.  Driving  fits  are 
adaptable  only  to  comparatively  small  diameters,  as  a  hammer  or 
sledge  is  usually  employed  to  drive  the  parts  together,  while 
the  forced  fits  involve  some  form  of  powerful  press.  Forced 
fits  also  are  adaptable. to  comparatively  small  diameters;  thus,  the 
driving  axle  of  a  locomotive  is  forced  into  the  hub  of  the  driving 
wheel,  but  the  tire  of  the  wheel  is  always  shrunk  onto  its  center. 
In  making  forced  fits  the  surfaces  are  coated  with  oil,  which  is 
of  course  not  done  in  shrink  fits. 

In  making  a  forced  fit  there  is  a  tendency  to  swage  the  metal, 
while  with  the  shrink  fit  the  bore  closes  squarely  down  upon  the 


LATHE  WORK  OX   FACE-PLATE,   ETC.  263 

center.  The  strains  produced  in  either  case  are  enormous.  With 
a  press  fit  it  is  very  important  that  the  parts  come  together 
squarely.  With  a  shrink  fit  the  bore  usually  expands  enough  to 
allow  the  shaft  to  enter  freely.  The  correct  placing  of  the  parts 
together  must  be  quickly  done,  as  otherwise  they  will  lock.  Should 
the  spindle  fail  to  enter  readily  or  stick  before  it  is  in  the  proper 
position,  it  must  be  instantly  driven  out.  This  may  result  from 
having  allowed  too  much  for  the  fit  or  from  not  heating  the  ring 
a  sufficient  amount. 

Forced  fits  being  made  with  oil  on  the  surfaces,  which  lubri- 
cates and  preserves  these  surfaces,  make  it  possible  to  remove 
by  pressure  the  spindle  when  desired.  With  shrink  fits  this  is  not 
always  possible,  the  surfaces  are  not  lubricated  and  frequently  the 
bore  is  heated  an  amount  sufficient  to  cause  a  scale  of  oxide  to 
form,  which  so  roughens  the  surface  that  it  clings  firmly.  If 
the  bore  is  small  the  shaft  can  usually  be  moved  by  heating  the 
ring  and  forcing  under  a  powerful  press.  The  shaft  should  be 
kept  as  cool  as  possible  while  the  ring  is  being  heated  by  appli- 
cation of  cold  water  as  close  to  the  ring  as  possible.  Care  and 
judgment  must  be  exercised,  and  even  then  the  surfaces  are 
quite  certain  to  be  injured  by  abrasion.  When  the  work  is  of 
large  diameter  and  the  center  can  readily  be  kept  cool  as  with 
the  locomotive  driving  wheel  the  ring  can  be  heated  until  it 
drops  off  from  its  own  weight. 

From  the  above  it  will  be  noted  that  for  work  of  large 
and  medium  diameter  the  shrink  fit  is  most  applicable  and  for 
work  of  smaller  diameter  the  forced  fit  is  best.  In  fact  on  small 
diameters  where  there  is  any  likelihood  of  ever  wishing  to  separate 
the  parts  the  shrink  fit  should  not  be  used. 


CHAPTER  XIX. 

BORING    AND    TURNING    MILLS. 

Boring  and  turning  mills  constitute  a  special  line  of  machine 
tools  made  necessary  by  modern  methods  of  manufacture  where 
large  numbers  of  similar  parts  are  to  be  handled  and  machined 
in  an  economical  manner.  In  Fig.  377  is  shown  a  3o-inch  boring 


FIG.  377. 

and  turning  mill  of  the  vertical  pattern.     This  represents  the 
smallest  size  machine  of  this  class  regularly  built. 

A  comparison  of  this  machine  with  an  engine  lathe  reveals  the 
same  characteristic  elements  in  both.  It  is  virtually  a  face  plate 
lathe  standing  on  end;  the  bed  and  upright  corresponding  to 
the  head  stock  and  bed  of  the  lathe.  The  spindle,  face  plate  and 
driving  mechanism  bear  a  close  resemblance  in  both  machines 
and  the  cross  rail,  frame  and  slider  on  the  boring  mill  correspond 


BORING   AND   TURNING  MILLS.  265 

with  the  carriage  and  compound  rest  on  the  lathe.  For  heavy 
work  the  structural  advantages  of  the  boring  mill  are  much  su- 
perior to  those  of  the  lathe.  The  form  of  the  machine  gives 
greater  rigidity  and  as  the  work  rests  upon  a  horizontal  table 
more  liberal  bearings  can  be  provided  than  is  the  case  with  the 
lathe,  at  the  same  time  overcoming  the  heavy  overhanging  parts. 
The  ease  with  which  work  can  be  set  up  and  adjusted  on  the 
horizontal  table  is  a  great  point  of  advantage. 

In  Fig.  378  is  shown  a  sectional  view  of  the  spindle  and  table 
bearing  on  the  mill,  shown  in  Fig.  377.  This  large  angular  bear- 
ing has  a  self-centering  tendency  which  tends  to  preserve  align- 


ment. This  form  of  table  bearing  as  well  as  the  flat  and  V  bear- 
ings employed  on  other  machines  of  this  class  provides  a  very  lib- 
eral bearing  surface;  the  ordinary  weight  load  due  to  table  and 
work  seldom  exceeding  25  to  30  pounds  per  square  inch  of  bear- 
ing surface.  Where  a  flat  bearing  of  large  diameter  is  employed, 
some  builders  provide  a  means  of  raising  the  table,  for  fast  run- 
ning, from  this  bearing  and  running  it  in  its  spindle  bearings, 
using  the  end  of  the  spindle  for  a  step  bearing.  The  small  sized 
machines  are  usually  provided  with  turret  heads,  either  plain  or 
swivel.  Automatic  feed  in  all  directions  with  feed  knock  off  is 
usually  provided. 

In  Fig.  379  is  shown  a  vertical  boring  mill  of  the  larger  class. 
The  tool  shown  swings  fourteen  feet  in  diameter.  It  is  also 
made  to  swing  twenty  feet  by  using  an  extended  base  upon  which 


266 


MODERN   MACHINE   SHOP   TOOLS. 


the  housings  are  so  mounted  that  they  may  be  moved  back  from 
the  center  of  the  table.  In  the  extended  machines  a  radial  arm 
mounted  upon  the  cross  rail,  carries  a  boring  bar  which  is  used 


FIG.   379. 

for  the  hub  work  while  the  other  heads  are  operating  on  the  out- 
side portions  of  the  work. 

In  Fig.  380  is  shown  a  standard  horizontal  boring  and  drilling 
machine.  The  range  of  adaptability  of  these  tools  is  large,  mak- 
ing them  excellent  tools  for  general  work.  The  work  to  be  oper- 


FIG.  380. 


BORING    AND    TURNING  MILLS.  267 

ated  upon  is  secured  to  the  table  which  is  adjustable  in  three  dir^c- 
tions,  thus  making  it  possible  to  bring  any  part  of  the  work  sur- 
face into  position  to  be  operated  upon  by  a  tool  held  in  the  boring 
bar.  Graduated  dials  on  all  of  the  table  operating  screws  make 
exact  spacings  for  holes  in  the  work  possible,  a  most  valuable 
feature  on  many  classes  of  work.  For  through  work,  as  in  the 
boring  of  cylinders,  the  bar  is  sufficiently  long  to  extend  through 
the  outer  support,  a  suitable  cutter  head  being  secured  on  the 
bar  to  carry  the  cutting  tools.  In  the  case  of  bores  too  small  to 
allow  the  main  boring  bar  to  pass  through,  smaller  bars  fitted  to 
the  tapered  bearing  in  the  end  of  the  main  bar  and  fitting  bush- 
ings in  the  outer  support  are  used.  The  facing  head  shown  at- 


FIG.  381. 


tached  to  the  nose  of  the  spindle  may  also  be  secured  to  the  bar 
at  any  point,  thus  making  it  possible  to -face  either  end  of  work 
that  the  bar  passes  through.  These  machines  may  be  advantage- 
ously used  for  heavy  plain  milling  work. 

Another  form  of  horizontal  boring  and  drilling  machine  is 
shown  in  Fig.  381.  Here  the  work  table  is  mounted  upon  the 
bed  and  the  vertical  adjustment  is  obtained  by  moving  the 
spindle  vertically  over  a  substantial  upright.  The  outer  bearing 
is  geared  with  the  head,  thus  causing  it  to  move  with  the  spindle. 
Automatic  table  feed  adds  much  to  the  convenience  of  this  tool 
for  general  work. 


268 


MODERN    MACHINE      SHOP    TOOLS. 


For  very  heavy  work  it  is  frequently  better  to  secure  the  work 
to  a  solid  bed  and  give  all  adjustments  to  the  spindle.  Such  a 
tool,  commonly  known  as  a  floor  boring,  drilling  and  milling  ma- 


FIG.  382. 


FIG.  383. 


BORING    AND    TURNING    MILLS.  269 

chine  is  shown  in  Fig.  382.  The  construction  of  the  machine  is 
evident  from  the  figure.  Automatic  cross  and  vertical  feeds  are 
provided  for  milling.  In  Fig.  383  is  shown  an  example  of  a  floor 
boring  mill  at  work  on  a  machine  frame. 

In  the  floor  boring  and  drilling  machine  of  Fig.  384  a  uni- 
versal tilting  table  is  provided.  When  fitted  with  a  revolving 
table,  operations  can  be  performed  on  all  sides  and  at  any  angle 
on  a  piece  of  work,  the  bottom  excepted,  without  changing  its 
setting. 

Cylinders  may  be  bored  in  the  lathe  in  the  vertical,  horizontal 


FIG.  384. 

or  floor  boring  machines,  but  when  a  large  amount  of  that  class 
of  work  is  to  be  done,  a  special  cylinder  boring  machine,  an  ex- 
ample of  which  is  shown  in  Fig.  385,  is  generally  employed.  In 
this  machine  only  those  features  of  the  horizontal  mill  necessary 
for  the  required  work  are  retained.  A  heavy  boring  bar,  rigid 
outer  support,  double  facing  head  and  no  vertical  adjustment 
are  the  usual  characteristics  of  these  tools.  The  work  is  usually 
held  in  a  suitable  jig  which  permits  of  rapid  setting. 

In  securing  work  to  the  table  of  the  vertical  boring  mill,  the 
same  care  and  methods  are  employed  as  with  the  lathe.     When 


270 


MODERN    MACHINE    SHOP   TOOLS. 


possible  the  work  is  held  in  chuck  jaws  or  in  special  drivers,  as 
shown  in  Fig.  367.  The  latter  method  has  the  advantage  of  not 
tending  to  spring  and  affect  the  circular  truth  of  the  work  and 
leaves,  as  in  balance  wheel  turning,  both  edges  of  the  rim  free  to 
operate  upon.  The  turning  and  boring  tools  used  in  machines  of 


FIG.  385. 

this  class  are  quite  similar  to  those  employed  in  engine  lathe  work, 
the  grinding  of  the  cutting  edges  being  the  same  for  similar 
work.  The  same  boring  bars,  reamers  and  formed  facing  tools 
used  in  turret  lathes  may  be  used  in  the  vertical  mill. 

For  cylinder  boring  work  in  the  horizontal  mill,  the  cutters  are 


FIG.  386. 


usually  carried  in  a  special  head  which  fits  over  the  main  boring 
bar  and  may  be  keyed  and  clamped  at  any  position  in  its  length. 
A  head  of  this  description  is  shown  in  Fig.  386.  The  cutting 
tools,  usually  two  or  four  in  number  are  clamped  in  position  and 


BORING   AND   TURNING    MILLS. 


271 


should  be  supported  as  far  out  as  possible.  These  tools  are 
preferably  of  self  hardening  steel  ground  to  proper  form  from 
the  bar  stock  without  forging. 

In  Fig.  387  is  shown  the  method  of  boring  and  facing  a  gas 
engine  cylinder  in  the  horizontal  boring  mill.  The  yoke  jigs  or 
frames  holding  the  work  are  securely  bolted  to  the  table  and  the 
work  held  by  two  set  screws  in  each  yoke.  By  means  of  these 
screws,  and  the  table  adjusting  screws,  the  work  can  be  trued 


FIG.  387. 

concentrically  with  the  bar.  The  head  shown  in  Fig.  386  is  passed 
through  the  bore  on  a  moderately  fine  feed  and  removes  the  most 
of  the  stock,  the  cut  being  divided  between  two  or  more  cutters. 
A  sizing  cut  is  then  taken  back  through  the  bore  leaving  only  a 
small  amount  for  the  finishing  cut.  As  the  scale  and  sand  has 
been  removed  by  the  first  or  roughing  cut,  a  somewhat  quicker 
speed  can  usually  be  employed  on  the  sizing  cut.  As  this  cut  is 
intended  as  a  truing  or  sizing  cut,  the  feed  should  not  be  too 
coarse. 

The   finishing   tool   is   next   placed   in    the   head   and   passed 


272  MODERN    MACHINE    SHOP    TOOLS. 

through  on  a  coarse  feed.  This  tool  should  have  a  broad  cutting 
edge,  very  slightly  rounded  in  its  length;  should  be  ground  with 
very  little  clearance  and  stoned  true  and  smooth.  Its  cut  should 
be  a  light  one  and  the  cutting  speed  well  within  the  safe  limit  for 
the  steel  employed.  The  object  of  the  coarse  feed  is  to  dis- 
tribute the  cut  over  a  greater  length  of  tool  edge  and  to  perform 
the  work  with  the  fewest  number  of  revolutions  possible,  thus  re- 
ducing the  wear  on  the  cutting  edge  to  a  minimum  and  produc- 
ing a  parallel  bore.  Where  a  number  of  bores  are  to  be  finished 
to  approximately  the  same  diameter,  it  is  advisable  to  have  the  fin- 
ishing tool  set  in  an  independent  head  which  can  be  substituted 
for  the  regular  head.  This  virtually  corresponds  to  a  reamer  and 
makes  possible  very  close  duplication  of  bores. 

The  end  of  the  cylinder  is  next  faced  with  the  facing  head 
shown,  and  if  desired  the  holes  for  the  cylinder  head  studs  may 
be  drilled  and  tapped  by  operating  the  cross  and  vertical  table 
adjustments  and  using  a  drill  and  tap  in  the  main  bar.  Where 
a  number  of  cylinders  are  to  be  bored  it  is  usually  found  more 
economical  to  do  the  drilling  and  tapping  in  a  smaller  machine. 


CHAPTER   XX. 

PLANING    AND    SHAPING    MACHINES. 

Their  Tools  and  Attachments. 

The  planer  and  shaper,  with  their  modifications  the  slotting 
machine  and  key-seatcr,  constitute  a  distinct  class  of  machine 
tools,  the  office  of  which  is  to  machine  plane  and  irregular  sur- 
faces that  can  be  most  readily  machined  by  a  straight-line  cut. 
Although  a  considerable  amount  of  work  that,  until  a  few  years 
ago,  was  classed  as  planer  and  shaper  work  has  been  turned  over 
to  the  milling  machine,  there  still  remains  a  very  wide  range  of 
work  that  must  continue  as  planer  and  shaper  work.  These  tools 
bear  to  the  machining  of  plane  surfaces  practically  the  same  re- 
lationship that  the  lathe  does  to  the  machining  of  round  work. 
The  cutting  tools  used  on  the  planer  and  shaper  are  practically 
the  same  as  those  used  on  the  lathe,  and  the  general  principles  in- 
volved in  the  operating  of  the  machines  are  quite  similar. 

The  planer  and  shaper,  although  used  on  the  same  class  of 
work,  differ  materially  in  design.  In  the  planer  the  work  moves 
to  the  tool,  while  with  the  shaper  the  tool  moves  over  the  work. 
In  the  planer  the  vertical  and  lateral  feeds  are  given  to  the  tool, 
while  on  the  shaper  the  lateral  feed  is  usually  given  to  the  work, 
the  vertical  feed,  however,  being  given  to  the  tool.  In  what  is 
known  as  the  traverse  head  shaper,  both  feeds  are  given  to  the 
tool  and  the  work  is  held  perfectly  stationary. 

In  Fig.  388  is  shown  a  standard  modern  planer.  The  bed  is 
deep  and  heavy  with  the  work  table  moving  in  inverted  vees. 
The  housings  or  uprights  are  secured  firmly  to  the  bed  and  cross- 
tied  at  the  top.  The  cross  rail  is  gibbed  to  the  front  of  the  hous- 
ings and  carries  the  tool  head.  The  cross  rail  is  adjustable  verti- 
cally, being  operated  by  the  two  elevating  screws,  by  hand  on  the 
smaller  machines,  and  by  power  on  the  larger  ones.  On  the  large 
machines,  two  heads  are  frequently  used  on  the  cross  rail  and  one 
on  the  face  of  each  housing,  thus  enabling  several  cuts  to  be 
taken  on  the  work  at  the  same  time. 

The  important  features  of  the  planer  are  its  table  driving  mech- 
anism including  reversing  gear  and  the  mechanism  for  operating 


274 


MODERN    MACHINE    SHOP    TOOLS. 


the  feeds.  In  some  of  the  earlier  planers  the  table  was  driven  by 
a  quick-pitch  screw  with  suitable  gears  and  pulleys  at  the  end  of 
the  bed.  This  method  has  been  entirely  replaced  by  the  rack  and 


FIG.  388. 

gear  drive  and  the  Sellers  or  spiral  gear  drive.     In  Fig.  389  is 
shown  the  gear  arrangement  as  commonly  used  in  the  rack  and 


1 


1  "  |D 

1 

U  -  

E3 

r  B 

i 

i 

\ 

I 

c  — 

—  F—  TE- 

3 

FIG.  389. 


PLANING    AND    SHAPING    MACHINES.  275 

•gear  drive.  The  rack  A  is  secured  to  the  bottom  of  the  table. 
The  gear  B  meshes  with  the  rack  and  is  driven  from  the  pulley 
C  through  the  gear  reductions  E  F  and  B  H.  D  and  I  are  loose 
pulleys  carrying  belts  that  run  in  opposite  directions.  When  the 
belt  running  in  the  direction  of  the  arrow  is  on  the  pulley  C  the 
table  and  work  move  toward  the  tool,  and  when  the  reverse  belt 
is  thrown  upon  C  the  table  moves  the  work  away  from  the  tool. 
The  backing  belt  is  usually  driven  at  about  four  times  the  velocity 
'of  the  forward  belt,  thus  giving  the  table  what  is  termed  a  quick- 
return  motion.  The  object  of  this  is  to  get  the  table  and  work 
back  and  ready  for  another  cut  with  the  least  possible  loss  of 
time.  As  applied  to  the  planers  by  different  makers,  this  mech- 
anism differs  somewhat  in  its  arrangement,  but  in  all  cases  is  a 
simple  geared  reduction. 

The  reversing  mechanism  differs  materially  on  the  various 
machines.  That  used  by  the  Gray  Company  on  the  planer  shown 
in  Fig.  388  illustrates  one  of  the  simpler  methods.  As  quite 
clearly  shown,  the  belt-shifting  rings  are  attached  to  a  pair  of 
arms  controlled  by  cams.  The  dogs,  which  clamp  to  the  side  of 
the  table  at  any  point  in  its  length,  engage  the  shipper  lever  on 
forward  and  return  strokes,  through  the  connecting  rod,  and 
move  the  cam  plate  and  belt  arms.  The  motion  is  such  as  to 
cause  the  belt  driving  to  be  shifted  from  the  tight  pulley  before 
the  other  belt  is  shifted  on,  thus  preventing  both  belts  from  get- 
ting on  to  the  tight  pulley  at  the  same  time.  As  these  belts  must 
be  shifted  very  quickly  and,  when  the  table  is  making  short 
strokes,  very  often,  it  is  quite  necessary  that  the  belts  be  narrow 
and  run  at  a  high  velocity.  These  belts  will  not  shift  properly  if 
run  too  tight,  and  should  always  be  of  the  best  grade  of  double 
leather  belting  in  order  to  stand  the  wear  and  pressure  on  the 
^dges.  As  it  is  frequently  necessary  to  run  the  work  out  from 
under  the  tool  to  take  measurements,  and  it  is  not  desirable  to 
change  the  position  of  the  dogs,  the  shipper  lever  is  provided  with 
a  trip  stop  which  can  be  raised,  to  allow  the  dog  to  pass  over 
without  changing  its  position.  The  planer  cannot  be  depended 
upon  to  stop  its  table  at  exactly  the  same  place  each  stroke.  This 
variation  may  arise  from  changes  in  the  pressure  of  the  cut,  but 
more  frequently  from  changes  in  the  speed  of  the  belts,  thus  vary- 
ing the  time  in  which  the  inertia  of  the  rotating  parts  is  over- 
come each  time  the  belt  is  shifted. 

In  Fig.  390  is  illustrated  a  planer  with  a  spiral  geared  or 


276 


MODERN    MACHINE    SHOP    TOOLS. 


Sellers  drive,  and  the  planer  shown  in  Fig.  394  also  has  a  drive  of 
this  description. 

As  shown  in  Fig.  391  the  mechanism  for  driving  the  table  is 
simple.  A  spiral  pinion,  usually  having  a  quadruple  thread,  en- 
gages a  rack,  the  teeth  of  which  are  at  right  angles  to  the  length 
of  the  table.  This  throws  the  axis  of  rotation  of  the  pinion  away 
from  the  line  of  motion  of  the  table  an  amount  equal  to  the  spiral 
angle  of  the  teeth  in  the  pinion  and  carries  the  pinion  shaft  at  this 
angle  through  the  side  of  the  bed.  This  gives  a  broad  bearing 
between  the  teeth  of  the  pinion  and  rack  and  causes  the  line  of 
pressure  to  come  directly  in  the  line  of  the  table's  motion/  Suit- 


able  bevel  gearing  and  tight  and  loose  pulleys  on  the  outer  end 
of  the  shaft  complete  the  driving  mechanism.  This  drive  is  noted 
for  its  smoothness  of  action,  and  freeness  from  the  vibration  fre- 
quently found  in  spur  gear  drives. 

The  mechanism  for  operating  the  feed  is  comparatively  sim- 
ple on  most  planers,  the  same  mechanism  usually  operating  both 
vertical  and  cross  feeds  on  the  cross  rail  head,  or  heads  when 
more  than  one  are  used.  As  the  amount  of  feed  adjustment  per 
stroke  must  be  constant  and  as  the  length  of  the  stroke  varies,, 
it  is  necessary  that  the  feed-operating  device  give  the  full  amount 
of  feed  adjustment  during  a  relatively  small  amount  of  the  table's 
stroke.  In  fact,  the  shortest  stroke  it  is  possible  to  have  the  table 


PLANING   AND    SHAPING    MACHINES. 


277 


make,  should  give  the  full  feed  adjustment  for  each  stroke.  In 
Fig.  388  the  arrangement  shown  is  simple  and  effective  and  in 
modified  forms  is  largely  used  by  the  different  builders. 

The  head  which  operates  the  feed  is  driven  by  the  extended 


Rack 


FIG.  391. 

pinion  shaft,  the  arrangement  of  parts  being  as  shown  in  Fig. 
392.  The  disc  A  is  secured  to  the  shaft  and  consequently  ro- 
tates with  the  pinion,  right  or  left  handed  rotation  depending 
upon  the  direction  in  which  the  table  is  moving.  The  disc  car- 
ries a  casing  B  and  cover  C,  the  cover  being  held  to  B  with  the 


three  studs  D  D  D  and  against  the  friction  washers  E  and  F  with 
a  uniform  pressure  by  the  spiral  springs  under  the  nuts  on  the 
studs.  If  the  casing  is  relieved,  it  and  the  cover  C,  together  with 
the  wrist  pin  G,  rotate  until  the  casing  is  again  held.  In  the  back  of 
the  casing  is  a  slot  H  into  which  the  stationary  pin  I  extends. 


278 


MODERN    MACHINE    SHOP    TOOLS. 


The  length  of  this  slot  is  determined  by  the  amount  of  casing 
rotation  required.  In  action,  the  table  starts  on  its  stroke;  B 
and  G  rotate  until  I  strikes  the  end  of  the  slot  H  and  the  rack 
has  been  moved  up  or  down,  depending  upon  which  side  of  the 
center  the  pin  G  is.  As  the  table  continues  its  stroke,  the  disc 
A  slips  between  the  washers  E  and  F,  and  G  remains  stationary. 
When  the  table  starts  on  its  return  stroke,  A  rotates  in  the  oppo- 
site direction,  carrying  with  it  B  and  G  until  the  pin  strikes  the 
other  end  of  the  slot,  the  rack  having  received  motion  in  the  op- 
posite direction  to  that  given  on  the  forward  stroke.  Thus  the 
rack  is  moved  up  and  down  once  each  time  the  table  moves  for- 
ward and  back,  and  the  amount  of  the  rack  motion  depends  upon 
the  distance  B  is  from  the  center  and  is  independent  of  the  length 

of  the  table  stroke.  A  pinion  X 
gears  with  the  rack  and  through 
a  shaft  carries  the  gear  A,  Fig. 
393.  Gear  B  rotates  free  on  the 
shaft,  gears  with  C,  and  on  its. 
face  carries  the  double  pawl  D. 
If  the  lower  foot  of  this  pawl,  as 
it  stands  in  the  cut,  is  thrown 
in,  it  slips  on  the  up  stroke  of 
the  rack,  but  drives  the  gear  B 
in  the  direction  of  the  arrow  on 
the  down  stroke.  If  the  upper 
foot  is  thrown  in  it  slips  on  the 
down  stroke  and  carries  gear  B 

in  the  opposite  direction,  the  direction  of  feed  being  reversed. 
It  is  evident  that  with  the  wrist  pin  G,  Fig.  392,  on  the  same  side 
of  the  center,  the  feed  occurs  at  the  beginning  of  the  forward 
stroke  when  the  feed  is  in  one  direction,  and  reversal  of  the  feed 
makes  it  occur  at  the  beginning  of  the  return  stroke.  The  wear 
on  the  feed  mechanism  is  least  when  the  feed  occurs  at  the  be- 
ginning of  the  return  stroke,  as  it  is  not  then  necessary  to  move 
the  tool  while  cutting.  On  the  other  hand,  feeding  on  the  return 
stroke  makes  the  wear  on  the  tool-  in  dragging  back  somewhat 
greater.  When  the  heads  are  attached  to  the  face  of  the  hous- 
ings, they  are  given  a  vertical  feed  on  the  housing  in  a  manner 
similar  to  that  already  described.  By  removing  the  gear  C  from 
the  cross  screw  and  putting  it  on  the  feed  rod,  the  vertical  feed  is 
operated  in  a  manner  similar  to  that  for  the  horizontal  feed. 


FIG.  393. 


PLANING    AND    SHAPING    MACHINES. 


The  size  of  a  planer  is  determined  by  the  length  of  its  table, 
the  distance  between  housings  and  the  maximum  distance  be- 
tween table  and  bottom  of  cross  rail.  The  extension  side  planer 
is  so  constructed  that  the  housing  on  the  side  opposite  the  driv- 
ing and  feed  mechanisms  can  be  extended  out  over  the  widened 
bed.  In  this  tool,  the  capacity  is  increased  by  spreading  the  hous- 


FIG.  394. 

ings,  an  extra  long  cross  rail,  of  course,  being  required.  This 
class  of  planer  is  of  value  in  shops  where  only  a  small  per  cent  of 
the  work  done  requires  a  wide  planer.  Another  modification 
known  as  the  open-side  planer  is  shown  in  Fig.  394.  In  this  tool 
one  housing  is  dispensed  with  entirely.  The  cross  rail  being 
heavy,  strongly  braced  and  carried  on  heavy  housings  on  the 
one  side  removes  the  width  limit  on  the  work  to  be  machined. 


280 


MODERN    MACHINE    SHOP    TOOLS. 


When  the  work  is  very  wide  and  overhangs  the  table  by  an  ex- 
cessive amount  it  is  necessary  to  provide  some  form  of  out-board 
support  for  the  outer  portion  of  the  work  to  rest  upon. 

On  all  planers  the  cross  rail  is  elevated  by  two  square-thread 
screws  set  in  the  face  of  the  housings  and  geared  together  at  the 
top.  These  screws  are  preferably  right  and  left  handed  and  must 
fa?  very  accurately  cut,  as  otherwise  the  cross  rail  will  not  remain 
parallel  to  the  table  in  its  width  at  all  positions.  On  the  larger 


o 
o 


FIG.  395. 


o 


FIG.  396! 


sizes  where  the  cross  rails  usually  carry  two  heads  and  are  very 
heavy  the  elevating  screws  are  operated  by  power  belted  from 
the  countershaft. 

The  form  of  bed  shown  in  Fig.  388  is  the  one  known  as  the 
deep  box  bed  and  is  now  quite  generally  used.  It  is  strongly 
ribbed  and  its  form  is  such  as  to  make  it  very  strong  and  rigid. 
The  form  of  table  guide  quite  exclusively  used  on  planers  is 
known  as  the  inverted  "V."  In  any  planer  it  is  very  important 
that  these  guides  be  most  carefully  fitted  and  suitable  means  pro- 


PLANING    AND    SHAPING    MACHINES.  28l 

vided  for  their  lubrication.  The  bearing  surfaces  are  usually 
grooved  to  retain  and  distribute  the  oil  with  suitable  wipers  pro- 
vided to  carry  the  lubricant  to  these  surfaces.  In  Fig.  395  is 
shown  a  common  and  very  efficient  method.  An  oil  well  or 
pocket  is  cored  in  the  bed  near  the  center  of  the  table's  motion, 
and  a  pair  of  conical  rollers  carried  in  a  suitable  frame  and  held 
against  the  surface  by  a  spring  carries  the  oil  from  the  well  to 
the  surface  to  be  lubricated.  The  principal  difficulty  with  this 
arrangement  comes  when  the  table  is  worked  on  short  stroke  for 
a  considerable  length  of  time,  as  in  that  case  the  portion  over  the 
rollers  only  is  properly  lubricated.  On  long  strokes,  however, 
the  action  is  perfect. 

The  planer  table  is  always  provided  with  a  large  number  of 
holes  for  stops  and  for  bolting  the, work  to  the  table,  also  with 
suitable  T-slots.  These  holes  should  be  drilled  and  reamed  and 
the  T-slots  planed  or  milled  in  order  that  the  bolt  heads  may  move 
freely  in  them. 

Fig.  396  shows  a  side  view  of  a  planer  head.  This  same  gen- 
eral form  is  used  by  all  builders  on  both  the  planer  and  shaper. 
It  is  nothing  more  than  the  compound  rest  on  the  lathe,  having  in 
addition  the  tool  box  and  apron.  The  cross  rail  corresponds  to 
the  carriage  on  the*  lathe.  It  is  a  rigid  girder  that  contains  the 
cross-feed  screw  and  the  vertical  feed  rod,  and  upon  which  the 
saddle  travels,  it  being  securely  gibbed  to  the  cross  rail.  The 
swing  frame  pivots  at  the  center  of  the  saddle's  face  and  may  be 
clamped  at  any  desired  angle,  either  side  from  the  vertical,  the 
amount  of  the  angle  being  determined  by  graduations  either  on 
the  edge  of  the  frame  or  face  of  the  saddle.  The  slider  is  gibbed 
to  the  swing  frame  and  operated  by  the  feed  screw  shown  in  the 
figure,  either  automatically  or  by  hand.  The  automatic  feed  is 
accomplished  in  the  same  manner  as  for  the  compound  rest,  a 
section  of  which  is  illustrated  in  Fig.  243.  The  mechanism,  of 
course,  varies  somewhat  with  the  different  builders.  The  tool 
box  is  pivoted  to  the  slider  and  has  a  limited  amount  of  adjust- 
ment each  side  from  the  center,  being  clamped  rigidly  in  any  de- 
sired position  by  the  lock  bolts  shown.  The  apron,  which  fits 
neatly  in  the  tool  box,  is  pivoted  to  the  box  at  the  upper  forward 
corner,  thus  allowing  it  to  swing  outward  on  the  return  stroke 
and  prevent  the  tool  from  dragging  heavily  over  the  work  surface. 
The  tool  post  is  secured  to  the  apron.  The  office  of  the  tool  box 
is  to  allow  the  tool  to  swing  out  from  the  work  on  the  return 


282 


MODERN    MACHINE    SHOP    TOOLS. 


stroke  when  machining  side  surfaces.  It  is  evident  that  if  the 
tool  post  was  secured  to  an  apron  pivoted  directly  to  the  slider, 
the  tool  would  swing  straight  out  on  the  return  stroke,  which 
would  be  all  right  when  machining  top  surfaces.  If,  however, 
side  surfaces  were  machined,  the  tool,  in  swinging  straight  out, 
would  drag  up  over  the  surface  planed,  injuring  the  tool  and 
marring  the  surface.  When,  however,  the  apron  pivots  to  a  tool 
box  that  can  be  inclined  somewhat  away  from  the  work  sur- 
face, it  is  evident  that  the  point  of  the  tool  will,  upon  the  return 
stroke,  swing  out  from  the  work ;  but  if  the  top  of  the  tool  box  be 
inclined  toward  the  side  of  the  work,  the  tool  will  swing  into  the 
work  surface,  causing  trouble.  It  is  therefore  necessary  to  swing 
the  box  in  the  opposite  direction  when  changing  from  one  side  of 


FIG.  397- 

the  work  to  the  other.  The  tool  clamping  device  may  be  an 
ordinary  tool  post  as  used  on  the  lathe,  but  it  is  more  commonly  a 
pair  of  clamps,  as  shown  in  Fig.  397. 

What  is  known  as  the  standard  shaper  is  of  the  column  or  pil- 
lar pattern,  one  design  of  which  is  shown  in  Fig.  398,  with  several 
shaper  attachments  (to  be  described  later).  In  this  machine  the 
upright  is  called  the  column.  The  cross  rail  is  gibbed  to  its 
front  face  and  is  adjustable  vertically  by  a  suitable  elevating 
screw.  The  box  or  knee  is  secured  to  a  saddle  which  moves  over 
the  cross  rail.  The  ram  carries  the  tool  head  w'hich  is  in  every 
way  similar  to  the  one  described  above,  the  swing  frame  being 
pivoted  to  the  end  of  the  ram.  In  the  example  shown,  the  swing 
frame  is  rotated  by  means  of  a  worm  gear  and  hand  wheel,  which 
enables  its  operation  while  the  machine  is  in  motion,  a  most  con- 
venient method  of  shaping  out  concave  surfaces. 


PLAN  I  NCI    AND    SHAPING    MACHINES. 


In  all  shapers  the  ram  is  actuated  by  one  of  two  methods. 
The  geared  method  provides  for  a  rack  and  gear  drive  similar 
to  that  used  in  operating  the  table  in  the  planer.  It  is  simply  a 
geared  reduction,  the  quick  return  to  the  ram  being  accomplished 
by  either  the  use  of  a  smaller  backing  pulley  or  higher  belt  velo- 
city for  the  return  stroke.  This  drive  is  illustrated  in  Fig.  389. 

In  Fig.  399  is  shown  a  standard  pattern  shaper  having  a  rack 
and  gear  drive.  This  drive,  although  little  used  on  small  ma- 
chines, is  always  applied  on  the  larger  shapers.  Machines  of 
the  pattern  shown  in  Fig.  399  are  regularly  made  in  sizes  from 
1 6 -inch  stroke  up  to  48-inch  stroke. 

The  other  method  is  known  as  the  crank  drive,  in  which  a 


FIG.  398. 

crank  or  its  equivalent,  operated  by  a  suitable  system  of  gears, 
transmits  the  motion  to  the  ram.  The  use  of  the  simple  crank 
drive  has  been  superseded  by  crank  drives  which  involve  a  quick- 
return  motion.  With  the  simple  crank  motion,  not  only  is  tfie 
time  occupied  on  the  return  stroke  of  the  ram  equal  to  that  on 
the  forward  stroke,  but  the  relative  velocity  of  the  ram  varies 
greatly  between  the  beginning  and  the  end  of  the  stroke,  being 
much  more  rapid  at  the  middle  than  at  the  ends.  With  the  quick- 
return  motion,  however,  it  is  intended  to  reduce  the  time  during 
which  the  ram  is  on  its  return  stroke  and  thus  give  more  time  for 


284 


MODERN    MACHINE    SHOP    TOOLS. 


the  forward  or  cutting  stroke,  and  also  to  average  up  as  much 
as  possible  the  relative  velocity  of  the  ram  at  the  different  por- 
tions of  its  forward  stroke.  In  all  cases  the  power  is  communi- 
cated to  a  shaft,  usually  by  a  belt  running  on  a  stepped  cone, 
causing  it  to  rotate  at  a  uniform  rate  of  speed. 

Crank  shapers  as  regularly  made  run  in  sizes  from  1 4-inch 
to  3O-inch  stroke. 

.In  Fig.  400  is  shown  the  mechanism  commonly  known  as  the 
slotted  or  vibrating  link.  P  is  a  pinion  receiving  motion  from 


FIG.  399. 

the  belted  cone  at  a  uniform  rate  of  rotation,  and  gearing  with 
the  gear  G.  The  link  M  M  pivots  at  the  point  L  and  carries  at 
its  upper  end  the  rod  R  which  connects  with  the  ram  at  H.  A 
block  B  is  fitted  nicely  in  a  slot  S  in  the  link  and  is  carried  on 
the  pin  I  which  projects  from  the  face  of  the  gear  G.  The  path 
of  the  pin  is  a  a,  the  block  B  moving  up  and  down  in  the  slot 
and  causing  the  link  to  vibrate  about  L  through  the  limits  y  y, 
carrying  with  it  the  rod  R  and  the  ram.  If  G  rotates  in  the 


1'LAXIXi 


AND    SHAPING    MACHINES. 


285 


direction  shown  by  the  arrow  and  the  tool  end  of  the  ram  is  at  K, 
then  the  forward  part  of  the  stroke  occupies  that  portion  of  G's 
rotation  indicated  by  the  angle  x  and  the  return  portion  by  the 
angle  y.  It  is,  therefore,  evident  that  the  return  stroke  occupies 


FIG.   399A. 


FIG.  399B. 

much  less  than  one-half  of  the  revolution  of  G.  An  analysis  of 
the  mechanism  shows  the  motion  of  the  ram  to  be  much  more 
uniform  than  with  the  simple  crank,  the  velocity  being  faster 
at  the  beginning  and  end  of  the  stroke  and  slower  through  the 


286 


MODERN    MACHINE    SHOP   TOOLS. 


middle  portions.  As  more  of  the  time  of  each  revolution  is  oc- 
cupied by  the  cutting  stroke  with  the  quick  return  than  with  the 
simple  crank  motion,  the  velocity  of  the  cut  will  be  lower  and 
more  uniform,  thus  enabling  a  greater  number  of  strokes  per 
minute  to  be  taken  than  would  be  permissible  with  the  simple 
crank  motion.  By  carrying  the  pin  I  toward  its  center  of  rota- 
tion, the  length  of  the  stroke  may  be  shortened  by  any  desired 
amount. 

The  Whitworth  quick  return  motion,  as  illustrated  in  Fig.  401 


KIG.  400. 

is  very  largely  used  for  shaper  drives.  Referring  to  the  figure, 
P  is  the  pinion  that  transmits  the  power  to  the  gear  G,  causing 
it  to  rotate  at  a  constant  rate  of  speed.  G  rotates  upon  a  fixed 
stud  B  of  large  diameter.  The  crank  A  is  fixed  to  the  shaft  C 
which  has  a  bearing  in  B  eccentric  to  its  center.  A  pin  D  is 
fastened  in  the  face  of  the  gear  G  and  engages  in  the  slot  I  in 
the  back  of  the  crank,  thus  causing  the  crank  to  rotate  with  the 
gear.  A  pin  X  carries  the  end  of  the  connecting  rod  R  which 
transmits  the  motion  to  the  ram  at  Z.  The  path  of  D's  rotation 
is  about  the  center  of  B,  and  the  path  of  X  is  about  the  center 


1'LAMNG   AND   SHAPING    MACHINES. 


287 


W         U 


288 


MODERN    MACHINE    SHOP    TOOLS. 


of  C.  When  the  crank  is  in  the  position  shown,  the  lever  arm 
D  C  is  minimum,  and  since  D  rotates  at  a  uniform  rate  of  speed, 
the  velocity  of  X  will  be  greater  at  this  point  than  at  any  other 
point  in  its  rotation.  When  D  reaches  the  position  D',  the 
lever  arm  D  C  becomes  maximum  and  the  pin  X  is  moving  at 
its  slowest  rate.  While  X  is  going  from  W  to  W',  in  the  direc- 
tion of  the  arrow,  the  ram  Z  is  making  its  return  stroke  and  the 
pin  D  has  rotated  from  V  to  V'  or  through  somewhat  less  than 
one-half  of  its  revolution.  The  forward  stroke  is  made  while  R 


FIG.  402. 

moves  from  W'  to  W  and  D  from  V  to  V.  It  is  evident  from 
the  above  that  more  time  is  occupied  on  the  forward  than  on  the 
return  stroke. 

A  form  of  shaper  well  adapted  to  the  machining  of  long  pieces 
of  work  is  shown  in  Fig.  402.  In  this  tool  the  bed,  which  is 
long,  carries  the  knee  on  its  front  face  and  the  arm  which  corre- 
sponds to  the  ram  on  the  pillar  shaper  is  given  a  motion  length- 
wise of  the  bed,  the  tool  head  being  fed  automatically  in  or  out 
on  the  arm.  This  machine  differs  from  the  open-side  planer, 
as  illustrated  in  Fig.  394,  in  that  the  tool  moves  over 


PLANING    AND    SHAPING    MACHINES. 


289 


stationary  work,  whereas  the  work  moves  under  the  tool  in  the 
open  side  planer.  On  that  which  is  known  as  the  movable  head 
shaper,  illustrated  in  Fig.  403,  the  work  remains  stationary  and 
the  ram  is  mounted  in  a  saddle  gibbed  to  the  top  of  the  bed  and 
fed  over  the  work.  Shapers  of  this  class  are  most  excellently 


adapted  to  the  machining  of  widely  separated  surfaces  on  heavy 
pieces  of  work. 

In  the  classes  of  shapers  above  illustrated  the  cutting  stroke 
is  the  outward  or  push  stroke.  In  the  Morton  or  draw  stroke 
shaper  shown  in  Fig.  404  the  reverse  is  the  case,  as  the  tool  cuts 
on  the  inward  or  draw  stroke.  This  tool  has  been  very  success- 


290 


MODERN    MACHINE    SHOP    TOOLS. 


fully  used  on  heavy  work  and  long  strokes,  and  has  been  widely 
modified  by  its  builders  to  suit  special  conditions.  The  head 
alone,  attached  to  a  suitable  knee  plate  and  driven  by  flexible 
shaft,  rope  transmission  or  electricity,  is  quite  extensively  used 
a?  a  portable  shaper  to  be  clamped  to  the  work  that  is  to  be  ma- 
chined. 

Many  of  the  cutting  tools  used  on  the  planer  and  shaper  are 


FIG.  404. 

the  same  as  those  used  on  the  lathe,  as,  for  example,  the  side- 
cutting,  diamond  point  and  cutting-off  tools.  There  are,  how- 
ever, several  forms  specially  adapted  to  planing  operations.  The 
extended  nose  tool  shown  in  Fig.  405  is  used  for  cutting  key- 
ways  or  for  any  class  of  internal  work.  This  tool,  unless  short 
and  heavy,  springs  badly.  It  should  be  held  as  high  in  the  tool 
holder  as  permissible,  thus  reducing  the  spring  to  the  least  amount 
possible.  The  shape  of  the  cutting  edge  is  suited  to  the  character 
of  the  work  and  should  be  given  as  small  an  amount  of  bottom 


PLANING    AND    SHAPING    MACHINES. 


29I 


clearance  as  will  enable  it  to  take  hold  of  the  cut,  otherwise  it 
will  dig  into  the  work  badly.  The  Armstrong  planer  tool  shown 
in  Fig.  406  takes  the  place  of  several  forms  of  ordinary  planer 
tools,  as  top  roughing,  right  and  left  side  roughing  and  right  and 
left  under-cut,  all  as  shown  in  the  figure.  It  may  also  be  used  to 
hold  cutting-off  blades  or  formed  cutters  of  any  class.  A  tool 
of  this  kind  for  the  planer  possesses  the  many  advantages  of 


FIG.  405. 


FIG.  4O& 


FIG.    407. 


similar  tools  for  the  lathe  in  which  a  small  cutting  tool  of  self- 
hardening  steel,  ground  rather  than  forged  to  shape,  is  used. 

The  gang  tool  shown  in  Fig.  407  is  often  used  on  the  planer 
where  the  surface  to  be  machined  is  large  and  comparatively 
regular  in  outline.  It  consists,  as  shown,  of  several  tools  set  one 
back  of  another  in  a  suitable  head  held  in  the  tool  clamps  in  the 
usual  manner.  The  cutting  points  are  so  adjusted  that  each 
takes  the  regular  cut  desired  so  that  a  regular  feed  of,  say,  1-16 
inch  on  each  cutter  would,  on  a  gang  cutter  tool,  enable  the  head 


292 


MODERN    MACHINE    SHOP    TOOLS. 


to  be  fed  over  the  surface  one-fourth  of  an  inch  at  each  stroke 
of  the  work.  A  tool  of  this  class  carrying  a  roughing  and  a  fin- 
ishing cutter  must  not  be  depended  upon  to  produce  satisfactory 
work  when  good  machined  surfaces  are  required,  as  the  spring 
of  the  roughing  cutter  due  to  the  inequalities  of  the  work  surface 
is  communicated  to  the  finishing  cutter,  and  this  must  as  a  result 
produce  a  finished  surface  having  much  of  the  irregularity  of  the 
original  rough  one.  Single  tools  of  this  character  with  special 
formed  cutting  edges  are  much  used  on  special  work. 

Planer  and  shaper  tools  should,  almost  without  exception,  be 
ground  with  very  little  bottom  clearance.  The  rake  should  be 
suited  to  the  hardness  of  the  metal  being  machined.  It  is  ad- 
visable, when  possible,  to  have  the  cutting  edge  well  back  under 
the  head  so  that  the  spring  of  the  tool  and  head  will  not  cause 


atC 


FIG.  408. 


FIG.  409. 


the  cutting  edge  to  dip  into  the  work  surface ;  it  also  tends  to 
prevent  chattering.  This  point  is  illustrated  in  Fig.  408,  where 
at  A  is  shown  a  tool  whose  cutting  edge  is  well  ahead,  and  at  B 
one  with  the  cutting  edge  well  back.  The  dotted  lines  show 
the  path  the  cutting  edge  tends  to  follow  in  each  case,  due  to 
the  spring  of  the  tool  itself.  The  spring  of  the  head  tends  in 
each  case  to  let  the  point  into  the  work,  but  not  so  badly  in  the 
case  shown  at  B  as  at  A.  On  all  top  and  side  cuts  the  tool 
swings  out  and  away  from  the  work  surface  on  the  return  stroke. 
For  under  cuts,  however,  except  those  of  comparatively  slight 
angle  from  the  vertical,  where  the  head  can  be  angled  to  meet 
the  condition,  the  tool  must  be  held  from  swinging  out  on  the 
return  stroke,  as  it  would  in  that  case  cause  trouble,  lifting  the 
work  or  breaking  it,  the  tool,  or  the  head.  For  under  cuts  the 
tool  should  have  a  long  shank  extending  well  above  the  clarnp 
and  blocked  out  at  the  top  as  shown  in  Fig.  409.  As  the  tool 


PLANING    AND    SHAPING    MACHINES. 


293 


drags  back  heavily  in  such  cases,  the  wear  on  it  is  excessive. 
A  side  head,  due  to  its  position,  is  well  adapted  to  under-cut 
work.  Where  much  under-cut  work  is  to  be  done  and  a  side 
head  is  not  available,  or  owing  to  the  position  of  the  work  sur- 
face, not  adapted,  a  relieving  tool  similar  to  the  one  shown  in 
Fig.  410  can  be  made  at  a  small  expense.  In  this  tool  a  stud 
.projecting  from  the  side  of  the  shank  carries  a  small  tool  hold- 
ing collar,  which  can  rotate  on  the  stud  until  the  stop  A 
strikes  the  shank.  A  light  spring  S  bears  against  the  stop,  al- 
lowing it  and  the  tool  to  swing  back  from  the  work  on  the  re- 
turn stroke  and  bringing  it  back  again  for  the  beginning  of  the 
forward  stroke.  For  finishing  cuts  at  coarse  feeds  the  broad 
nose  tool  shown  in  Fig.  411  is  used.  The  corners  are  slightly 


FIG.  410. 


FIG.  411. 


rounded,  as  shown  at  A,  B,  and  the  tool  given  only  a   slight 
amount  of  clearance,  as  shown. 

The  planer  and  shaper,  when 'equipped  with  suitable  attach- 
ments, are  capable  of  a  very  wide  range  of  what  might  be  termed 
special  tooling  operations.  An  emery-grinding  head  is  secured  to 
the  cross  rail  with  suitable  belted  connections  to  drive  its  wheel 
and  the  planer  table  at  the  proper  speeds,  and  the  planer  is  con- 
verted into  a  very  creditable  plane  grinding  machine.  This 
transformation,  however,  is  not  to  be  advocated,  as  the  bearing 
surfaces  of  the  planer  are  not  properly  designed  for  the  pro- 
tection necessary  against  the  flying  particles  of  emery.  The  cor- 
version,  however,  into  a  plane  milling  machine  is  more  com- 
mendable, as  the  planer  when  provided  with  suitable  feeds  for 
the  table  is  fairly  well  adapted  to  milling  work.  In  Fig.  412  is 
illustrated  a  device  that  can  readily  be  attached  to  the  cross  riil 
of  any  planer,  virtually  converting  it  into  a  slab  milling  machine. 
The  head  of  this  attachment  is  so  constructed  that  the  spindle 


294 


MODERN    MACHINE    SHOP    TOOLS. 


can  be  swiveled  from  horizontal  to  vertical.  \s  there  are  many 
operations  that  can  be  more  advantageously  performed  by  milling 
than  by  planing,  an  attachment  of  this  kind  will  frequently  be 
of  value  in  cases  where  a  slab  milling  machine  is  not  available. 
In  Fig.  413  is  shown  an  attachment  for  planing  concave  or  con- 
vex surfaces.  It  consists  principally  of  a  vise  pivoted  in  suita- 
ble housings  at  the  points  O  O.  The  arm  S  is  a  part  of  the  vise. 


FIG.  412. 

and  carries  within  it  a  stud  terminating  in  the  guide  R.  The  bar 
G  G  is  secured  at  any  desired  angle  with  the  table  to  the  post  P, 
which  is  fastened  to  the  side  of  the  planer  bed.  If  G  G  is 
parallel  to  the  work  table  the  vise  will  have  no  motion  relative 
to  its  housing.  If  the  bar  is  set  as  shown  in  the  figure  the  farther 
end  of  the  vise  elevates  as  the  table  advances  to  the  cut  and  a 
concave  surface  results.  By  inclining  the  bar  in  the  opposite 
direction,  however,  the  end  drops  as  the  table  advances  to  the 
cut  and  a  convex  surface  results.  The  arc  of  the  circle  planed 
depends  on  the  amount  of  the  angle  between  G  G  and  the  table ; 


PLANING    AND    SHAPING    MACHINES. 


295 


the  greater  the  angle,  the  smaller  the  radius  of  the  surface  planed. 
With  the  bar  G  G  removed  the  vise  becomes  an  ordinary  planer 
vise,  possessing  the  additional  advantage  of  being  adjustable  to 


FIG.  413. 

quite  an  angle  with  the  work  table,  a  point  of  value  in  the  planing 
of  wedges. 

Planer  vises  are  very  necessary  accessories  to  both  the  planer 
and  shaper,  as  a  considerable  amount  of  planer,  and  more  es- 


FIG.  414. 

pecially  shaper  work  must  be  held  in  the  vise.  In  Fig.  414  are 
shown  two  forms  of  planer  vises.  The  vise  shown  at  A  has  a 
plain  base,  to  be  clamped  in  any  desired  position  on  the  planer 
table.  The  adjustment  of  the  movable  jaw  is  clearly  shown  in  the 


296  MODERN    MACHINE    SHOP    TOOLS. 

figure.  The  vise  shown  at  B  is  provided  with  a  circular  base 
usually  fitted  with  two  tongues  to  fit  the  wards  or  T  slots  in  the 
planer  table  and  thus  insure  its  being  put  on  at  the  same  angular 
position  with  the  line  of  the  table's  motion.  The  circular  bottom 
of  the  vise  is  pivoted  at  the  center  of  the  base  and  provided  with 
a  graduated  rim,  thus  making  it  possible  to  set  the  jaws  at  any 
desired  angle  with  the  table's  length.  In  this  vise  blocking  is 
used  between  the  clamping  screws  and  the  movable  jaw.  It  is 
quite  necessary  in  any  planer  vise  to  have  the  movable  jaw  so 
secured  that  it  can  be  clamped  down  closely  to  its  seat,  as  other- 
wise the  clamping  of  the  work  between  the  jaws  will  cause  it 
to  lift.  The  shaper  vise  is  considered  a  regular  shaper  attach- 
ment, and  is  always  furnished  with  the  machine.  The  sliding 
jaw  is  always  operated  by  a  screw  and  gibbed  to  the  body  of  the 
vise. 

The  attachment  shown  in  Fig.  415  is  a  special  tool  for  the 


FIG.  415. 

planing  of  circular  surfaces,  as,  for  example,  locomotive  driving 
boxes.  Its  range  is  comparatively  small.  The  long  shank  is  held 
in  the  regular  tool  clamps.  The  head  of  the  attachment  is 
pivoted  at  its  center  in  the  end  of  the  arm  and  operated  by  a 
shaft  carried  in  a  recess  in  the  back  of  the  arm.  A  worm  and 
worm  gear  at  the  upper  end  of  the  bar  provides  a  suitable  feed 
drive  for  rotating  the  tool.  When  a  considerable  amount  of  work 
is  to  be  done  with  the  attachment  a  suitable  automatic  feed  can 
readily  be  applied  to  the  worm. 

The  milling  machine  has  taken  most  of  the  center  work  away 
from  the  planer.  A  pair  of  planer  centers,  however,  an  example 
of  which  is  shown  in  Fig.  416,  is  frequently  of  great  value.  They 
are  usually  tongued  to  fit  the  wards  in  the  table,  and  the  head 
spindle  is  so  indexed  that  the  circle  can  be  divided  into  a  large 
number  of  equal  parts. 


PLANING    AX1)    SHAPING    MACHINES.  297 

In  Fig.  398  is  illustrated  a  number  of  shaper  attachments. 
The  one  shown  on  the  machine  is  for  planing  spirals.  The 
spindle  of  the  head  is  rotated  back  and  forward  with  the  strokes 
of  the  ram  through  a  suitable  geared  mechanism  operated  by 
the  up-and-down  motion  of  the  block  over  which  the  inclined 
guide  (which  is  actuated  by  the  stroke  of  the  ram)  slides.  The 
work  to  be  operated  upon  is  held  between  centers,  and  as  the 
upper  section  of  the  knee  can  be  inclined,  spirals  can  be  shaped 
upon  tapered  work.  The  shaper  vise  is  shown  at  the  rear  of  the 
cut.  Two  small  centers  attached  to  the  jaws,  as  shown,  are  fre- 
quently found  very  convenient.  The  vise  wedges  shown  on  the 
extended  base  of  the  shaper  are  pivoted  at  the  center  and  are 
used  against  one  of  the  jaws  of  the  vise  in  holding  tapered  work. 

In  the  front  and  on  the  left  of  the  cut  is  shown  a  convex 
shaping  attachment.     This  may  be  secured  to  the  front  of  the 
cross    rail    in    the    place    of   the 
knee,   and  the   feed   attached  to 
the      geared      feed      mechanism 
shown,  which  gives  the  circular 
table,  and  such  work  as  may  be 
clamped   on    it,   a    rotating    feed 
motion.     This  device  can  also  be  FIG.  416. 

secured  to  the  knee  in  a  horizon- 
tal position  for  operating  upon  special  work  requiring  the  ma- 
chining of  radial  surfaces. 

The  circular  attachment  shown  in  the  center  of  the  foreground 
is  provided  with  an  arbor  carrying  two  cones.  Work  having 
any  bore  within  the  limits  of  the  cones  can  be  held  on  the  at- 
tachment, an  automatic  feed  giving  the  work  feed  rotation.  The 
index  centers  shown  on  the  right  are  in  principle  similar  to  those 
shown  in  Fig.  416.  They  are,  however,  self-contained,  both  head 
and  tail  stock  being  secured  on  a  suitable  base  casting,  which  in 
turn  may  be  secured  to  the  knee  of  the  shaper.  In  Fig.  399  A 
is  shown  the  circular  attachment  as  used  on  the  "Cincinnati" 
shapers.  The  spindle  is  driven  by  a  worm  and  gear,  either 
by  hand,  or  automatically  by  the  power  feed  mechanism  shown. 
In  Fig.  399  B  is  shown  the  automatic  head  feed  used  on  this 
shaper.  It  is  a  positive  acting  mechanism,  having  a  variable  feed 
adjustment.  The  action  corresponds  to  that  used  on  the  planer 
head  feed,  the  short  side  shaft  corresponding  to  the  feed  shaft  in 


298  MODERN    MACHINE    SHOP    TOOLS. 

the  cross  rail  and  the  motion  is  transmitted  to  the  nut  by  two 
pairs  of  miter  gears. 

Spiral  planing  attachments  similar  to  the  one  shown  in  Fig. 
398  are  frequently  applied  to  planers  for  the  grooving  of  spiral 
rolls  and  work  of  that  class.  Another  attachment  for  the  cutting 
of  spirals  on  the  planer  consists  of  a  rack  secured  to  the  side  of 
the  planer  bed  at  about  the  height  of  the  surface  of  the  work 
table.  A  pinion  carried  on  a  shaft  running  in  bearings  secured  to 
the  surface  of  the  table  and  at  right  angles  to  its  length  gears 
with  the  rack.  This  cross  shaft  through  a  pair  of  bevel  gears 
transmits  its  motion  to  a  spindle  parallel  with  the  table's  length 
and  to  which  the  work  to  be  spirally  planed  is  attached.  The 
motion  of  the  table  causes'  the  shaft,  spindle  and  work  to  rotate 
at  a  rate  determined  by  the  velocity  ratio  of  the  gears. 

A  shaper  is  sometimes  used  for  key  seating  bores.  There  is  a 
vertical  supporting  knee  attached  to  the  table  for  holding  the 
work,  and  a  special  head  attached  to  the  ram  in  place  of  the 
ordinary  tool  box.  This  head  holds  a  cutter  bar,  which  is  in  the 
form  of  a  broach,  and  will  cut  the  keyway  at  one  stroke  of  the 
ram. 


CHAPTER  XXI. 

PLANER  AND  SHAPER   WORK. 

The  proper  securing  of  work  in  the  vise  or  on  the  shaper  or 
planer  table  for  planing  operations  is  a  most  important  step  in 
the  production  of  satisfactory  work.  As  the  variety  of  work  as- 
signed to  these  machines  is  great,  the  operator  continually  finds 
himself  against  a  new  problem  requiring  good  judgment  and 
care.  In  most  cases  much  more  skill  is  required  in  the  setting 
up  of  the  work  than  in  the  machining.  When  the  work  is  com- 
pact and  heavy,  and  the  amount  of  metal  to  be  removed  is  rela- 
tively small,  the  danger  of  springing  it  is  not  usually  great.  If, 
however,  the  work  is  large,  of  irregular  shape  or  light,  the 
danger  of  springing  is  great.  The  springing  is  due  to  two 
causes :  First,  by  ununiform  or  severe  clamping  which  distorts 
the  work  and  throws  the  machined  surfaces  out  when  it  is  un- 
damped ;  second,  the  removal  of  the  outer  surface  of  a  casting 
or  forging,  which  frequently  relieves  shrinkage  and  forging 
strains  and  throws  the  work  out  of  true.  The  first  of  these 
troubles  can  be  overcome  only  by  using  the  utmost  care  in  setting 
up  the  work,  and  the  second  by,  so  far  as  possible,  first  roughing 
off  all  surfaces  before  taking  any  finishing  cuts,  thus  allowing 
the  work,  after  the  roughing,  to  assume  its  normal  condition  as 
to  strains. 

The  most  important  consideration  in  the  clamping  of  work 
to  the  table  is  to  locate  the  points  of  clamp  pressure  directly  over 
the  points  of  support.  The  supports  should  be  firm  and  bear  as 
equally  as  possible  between  the  work  and  the  table.  When  only 
a  thin  shim  is  required  to  level  up  the  work,  it  should  preferably 
be  of  metal,  as  cardboard,  leather  or  any  compressible  material 
will  allow  the  clamp  to  spring  the  work.  Good  blocks  and  parallel 
bars  are  indispensable  in  the  planer  outfit.  For  work  where  the 
points  of  support  vary  in  height,  leveling  wedges  and  small  jack 
screws  are  most  excellent,  as  they  can  be  quickly  adjusted  to  any 
desired  height.  These  leveling  wedges,  especially  if  a  single 
wedge  is  used,  should  be  made  with  only  a  slight  taper.  In  Fig. 
417  is  shown  a  pair  of  these  wedges.  When  carefully  made  they 
form  a  good  support  and  may  be  used  to  make  the  fine  adjust- 


300 


MODERN    MACHINE    SHOP    TOOLS. 


ment  for  height  either  directly  on  the  work  table  or  on  top  of 
other  blocking.  The  planer  jacks  shown  in  Fig.  418  are  most 
excellent,  a  few  of  these  frequently  replacing  a  large  number  of 


FIG.  417. 
/ 

hlocks  of  miscellaneous  shapes  and  sizes.  A  good  set  of  planer 
bolts  should  be  found  on  each  machine.  Common  machine  bolts 
are  not  well  suited  to  this  purpose  as  the  heads  are  too  thick 


FIG.  418. 

and  not  large  enough  to  properly  fill  the  T-slot.  Planer  bolts  are 
preferably  made  of  mild  steel  with  heads  turned  to  required 
thickness  and  milled  on  the  four  sides  to  properly  fit  the  T-slot. 


The  clamp  is  usually  made  from  a  bar  of  flat  steel  with  one  or 
more  holes  drilled  in  it  for  the  bolt,  as  shown  in  Fig.  419,  and 
tapered  somewhat  on  the  work  end  to  more  readily  enable  it  to 


PLANER    AND    SHAPER    WORK. 


3OI 


be  placed  in  the  corners  of  the  work.  The  clamp  shown  in  Fig. 
420  is  made  from  square  iron  and  forms  a  substantial  and  con- 
venient form  of  clamp.  Clamps  of  this  character  should  be  ap- 
plied to  the  work  in  the  manner  shown  in  Fig.  421,  as  closely  as 


n 


FIG.  420. 


possible;  that  is,  the  bolt  should  stand  close  to  the  edge  of  the 
work  and  the  blocking  for  the  outer  end  of  the  clamp  as  far 
away  from  the  bolt  as  convenient,  thus  throwing  most  of  the  bolt 
pull  upon  the  work  and  not  upon  the  blocking,  as  would  be  the 


FIG.  421. 


FIG.  422. 


FIG.  423. 


case  if  the  bolt  was  nearer  the  blocking  than  the  work.  The 
T-slots  should  be  sufficiently  deep  to  prevent  any  reasonable  bolt 
pull  from  breaking  them  out.  This  danger  is,  however,  lessened 


302 


MODERN    MACHINE    SHOP    TOOLS. 


t>y  placing  the  work  or  its  point  of  support  as  close  up  to  the 
bolt  as  possible. 

If  the  entire  surface  of  the  work  is  to  be  machined,  clamps 
as  above  described  cannot  conveniently  be  used  as  it  would 
necessitate  changing  their  position  during  the  cut,  a  most  deli- 
cate operation  with  results  usually  unsatisfactory  if  a  true  surface 
is  required.  When  the  work  has  considerable  thickness,  small 
lugs  or  flanges  can  be  cast  on  the  edges  for  holding  the  clamp 
point  and  in  some  cases  a  drilled  hole  in  the  edge  of  the  work 
can  be  made  to  receive  the  point  of  the  clamp.  In  cases  where 
these  methods  are  not  convenient,  the  work  can  be  held  in  the 
manner  shown  in  Fig.  422.  Two  forms  of  post  are  shown  in 
this  figure,  the  one  a  plain  pin  to  fit  neatly  in  the  round  holes  in 
the  table  and  the  other  with  rectangular  base  and  tongue  to  fit 


FIG.  424. 

the  T-slots.  A  common  set  screw  with  cone  point  fits  any  of 
the  tapped  holes  in  the  post,  the  height  of  these  holes  varying  to 
suit  the  thickness  of  the  work  and  length  of  finger  used.  The 
fingers  are  cupped  to  receive  the  point  of  the  screw  and  the  work 
end  pointed  to  engage  a  prick-punch  hole  in  the  side  of  the  work 
or  preferably  formed  flat  as  shown  in  the  figure.  A  suitable  post 
to  receive  the  end  thrust  of  the  tool  must  in  all  cases  be  set  ahead 
of  the  work,  and  should  be  made  of  steel,  preferably  a  low  grade 
of  tool  steel,  to  insure  stiffness,  and  turned  to  fit  neatly  the  holes 
in  the  table.  It  should  extend  well  into  the  hole,  but  should  not 
reach  high  above  the  table,  from  two  to  four  inches  being  ample. 
The  shorter  it  is,  the  less  liable  it  is  to  get  bent.  In  Fig.  423  is 
shown  such  a  post.  The  two  holes  drilled  through  it  at  right 
angles  to  each  other  facilitate  turning  or  prying  it  up,  when,  from 
any  cause,  it  may* stick  too  tight  in  the  hole  to  be  pulled  out  with 
the  fingers. 


PLANER    AND    SHAPER    WORK. 


303 


Round  work  may  be  held  as  shown  in  Figs.  424  and  425.  In 
Fig.  424  the  bar  rests  on  the  edges  of  the  T-slot.  In  this  case 
the  edges  should  be  in  good  condition.  It  is  suitable  for  bars  of 
small  diameter  only,  while  with  the  method  shown  in  Fig.  425 
where  a  knee  plate  is  used  a  bar  of  any  diameter  can  easily  be 
held. 

A  pair  of  V-blocks  can  be  used  very  advantageously  for  hold-* 


FIG.  425. 


ing  round  work.  These  blocks  as  shown  in  Fig.  426,  should  be 
tongued  to  fit  the  wards  in  the  table  and  the  V-notches  planed 
with  the  blocks  in  place. 

A  good  knee  plate  is  frequently  quite  necessary  in  the  securing 


FIG.  426. 

of  work  on  the  planer  table.     The  regular  knee  on  the  shaper, 
however,  serves  the  purpose  on  that  tool. 

On  long  work  the  twisting/and  deflection  due  to  the  weight  of 
the  work  itself,  must,  trhere  accvwacy  is  required,  be  taken  carefully 


304  MODERN    MACHINE    SHOP    TOOLS. 

into  consideration.  For  example,  long  lathe  and  planer  beds  must 
in  the  machining  be  handled  with  great  care.  Take  a  lathe  bed 
that  is  to  rest  upon  legs  at  each  end.  It  should  have  the  seats 
upon  which  the  legs  are  bolted  planed  first,  the  points  of  sup- 
port being  not  at  the  extreme  ends  but  at  points  about  one-fourth 
the  bed's  length  from  each  end,  with  wedges  so  adjusted  as  not 
to  twist  the  bed  in  its  length.  After  planing  the  leg  seats  the 
bed  can  be  turned  over  and  clamped  directly  on  these  seats,  the 
bed  assuming  its  natural  deflection,  in  which  position  the  shears 
are  planed. 

In  securing  work  in  the  vise,  the  pressure  of  the  jaw  against 
the  work  should  be  as  uniform  along  the  surface  gripped  as  pos- 
sible. If  the  surface  is  somewhat  irregular  a  soft  packing,  as 
paper  or  leather,  will  equalize  the  pressure.  If  there  is  much 
irregularity,  however,  it  is  preferable  to  cause  the  vise  jaws  to 
grip  the  work  at  points  rather  than  throughout  their  entire 
length.  For  this  purpose  a  wedge  or  solid  block  should  be  used 
between  the  work  and  jaw  and  located  as  near  the  ends  of  the 
jaws  as  possible.  When  a  jaw  is  tightened  onto  the  work  its 
tendency  is  to  lift,  causing  the  work  to  lift  on  the  movable  jaw 
side.  For  this  reason  the  movable  jaw  should  be  fitted  nicely  to 
its  slide  with  bolts,  as  previously  shown  in  Fig.  414,  for  clamping 
it  firmly  after  gripping  against  the  work.  Planer  vise  jaws  are 
usually  made  of  cast  iron,  and  a  false  facing  of  soft  steel  secured 
with  bolts  to  these  jaws  is  excellent  when  finished  surfaces  are 
to  be  gripped  between  them.  It  is  important  for  nice  work  to 
keep  the  vise  jaws  in  good  condition. 

The  leveling  and  squaring  up  of  work  on  the  planer  table  is 
important.  If  the  work  has  been  laid  out  or  some  of  its  surfaces 
previously  machined,  the  surface  gauge  will  be  used  in  bringing 
these  lines  or  surfaces  parallel  with  the  table.  If  a  line  on  the 
work  is  to  be  set  parallel  with  the  line  of  motion  of  the  table,  the 
surface  gauge  needle  point  will  be  adjusted  to  the  line  at  one  end 
with  the  base  of  the  gauge  against  the  side  of  the  slider.  The 
table  is  then  moved  under  the  cross  rail  and  the  other  end  of  the 
line  brought  to  coincide  with  the  point  of  the  needle.  Another 
method  is  to  square  up  from  lines  that  have  previously  been 
planed  with  a  fine  sharp-pointed  tool  in  the  top  surface  of  the 
table,  and  with  the  caliper  divider  caliper  from  the  blade  of  the 
square  to  each  end  of  the  line  on  the  work ;  or,  if  this  line  is  not 
too  far  from  the  edge  of  the  planer  table,  the  calipering  may  be 


PLANER    AND    SHAPER    WORK.  305 

from  the  line  to  a  straight  edge  placed  against  the  side  of  the 
work  table.  When  the  line  on  the  work  surface  is  to  be  set  at 
right  angles  to  the  length  of  the  bed,  the  work  is  brought  close 
up  to  the  cross  rail  and  the  line  adjusted  to  the  surface  gauge 
needle  point,  with  the  base  of  the  gauge  resting  against  the  face 
of  the  cross  rail ;  or,  as  in  the  other  case,  the  caliper  divider  with 
a  straight  edge  placed  against  the  face  of  the  cross  rail  can  be 
used. 

In  the  manipulation  of  the  planer  and  shaper  the  beginner 
should  keep  a  few  points  closely  in  mind.  All  planers  and  geared 
shapers  do  not  have  a  fixed  length  of  stroke,  the  depth  of  the  cut 
and  the  speed  of  the  countershaft  affecting  slightly  the  points  at 
which  reversals  take  place.  Some  allowance  must  therefore  be 
made  for  the  overtravel  of  the  tool.  An  excessive  amount  of  over- 
travel,  however,  means  a  large  loss  of  time.  Roughing  cuts 
should  be  as  heavy  and  at  as  coarse  feeds  as  the  machine  will 
conveniently  handle  and  the  strength  and  character  of  the  work 
will  permit.  Before  planing  side  surfaces  see  that  the  top  of  the 
tool  box  is  inclined  from  the  work.  This  allows  the  tool  to  swing 
out  and  clear  the  work  surface  on  the  return  stroke.  If  it  is  not 
inclined  the  point  of  the  tool  drags  hard  on  the  work  surface,  and 
should  it  be  inclined  to  the  wrong  side  the  tool  will  swing  into 
the  work,  doing  much  damage.  Raising  the  tool  clear  of  the 
work  on  the  return  stroke  preserves  the  cutting  edge.  Means 
for  automatically  accomplishing  this  are  frequently  employed. 
Keep  the  cross  rail  clamped  firmly  to  the  housings  when  in  use 
and  parallel  with  the  table.  Before  putting  in  the  feed  see  that 
the  feed  gear  is  on  the  right  spindle,  as  otherwise  the  tool  may 
start  up  or  down  when  it  is  intended  to  move  across  the  work. 
As  there  are  usually  more  ways  than  one  to  do  every  piece  of 
work,  study  the  way  in  which  it  can  best  be  done.  The  manner 
in  which  the  work  is  set  up,  the  kind  of  tools  used  and  the  way 
in  which  they  are  ground,  as  well  as  the  efficient  handling  of  the 
machine,  all  have  an  important  bearing  on  the  quality  and  amount 
of  the  work  turned  out. 


CHAPTER    XXII. 

THE  SLOTTING  MACHINE  AND  KEY  SEATER. 

The  slotting  machine  is  illustrated  in  Fig.  427.  It  consists 
primarily  of  a  substantial  frame,  a  tool-carrying  ram  and  a  table 
for  supporting  jhe  work.  While  the  plane  of  the  table  is  the 


FIG.  427. 


same  as  on  the  shaper,  the  ram  moves  in  a  vertical  plane,  thus 
adapting  it  to  work  in  which  surfaces  at  right  angles  to  other 
surfaces  are  to  be  machined.  The  table  which  is  provided  with 
feed  rotation  is  mounted  upon  a  slider  and  this  in  turn  upon  a 


THE    SLOTTINC,    MACHINE    AND    KEY    SEATEK. 


307 


saddle  gibbed  to  the  knee  of  the  machine,  thus  providing  a  work 
table  that  may  be  rotated  or  moved  to  any  position  in  its  plane 
relative  to  the  cutting  tool  and  within  the  capacity  limits  of  the 
machine. 

The  slotter  is  very  largely  used  for  the  cutting  of  key  ways 
in  hubs  and  the  machining  of  rectangular,  circular  or  irregular 
outlines  which  cannot  readily  be  done  on  shaper,  lathe  or  mill- 
ing machine.  In  Fig.  428  is  shown  a  piece  of  work  well  adapted 
to  the  slotting  machine.  The  surfaces  a,  b,  and  c  can  be  ma- 
chined on  the  slotter  more  advantageously  than  on  the  planer  or 


FIG.  428. 

shaper,  as  the  side  rests  solidly  upon  the  table  and  the  form  of  the 
slotting  tool  is  adapted  to  the  job.  On  planer  or  shaper  a  knee 
plate  must  be  used  to  clamp  the  work  to,  and  an  extension  tool 
employed. 

The  half  boxes  used  on  locomotive  driving  axles  as  shown  in 
Fig.  429  illustrate  another  slotter  job.  Here  the  cylindrical  bear- 
ing surface  is  machined  by  placing  the  work  concentric  with 
the  work  table.  The  table  is  so  placed  with  reference  to  the  tool 
that  the  necessary  amount  of  rotation  can  be  obtained  without 
interfering  with  the  tool  or  head.  After  each  downward  or  cut- 
ting stroke  the  table  is  automatically  rotated  the  necessary  amount 
of  feed  for  the  next  cut.  By  using  a  fine  feed  and  a  properly 


308 


MODERN    MACHINE    SHOL"    TOOLS. 


formed  cutting  edge  on  the  tool  very  smooth  true  surfaces  result. 
Connecting-rod  ends  and  crank  eyes  are  advantageously  ma- 
chined on  the  slotter. 

The  tools  for  the  slotter  are  either  forged  on  the  end  of  heavy 
square  bars  of  steel  or  inserted  in  steel  bars  of  either  square  or 
round  section.  When  forged  the  tool  is  usually  of  the  form 
shown  in  Fig.  430.  The  cutting  angles  are  the  reverse  of  those 
of  lathe  and  planer  tools.  The  end  angle  turns  the  chip  and  is 
the  angle  of  rake  with  x  as  the  angle  of  clearance.  As  with 
planer  tools  the  angle  of  clearance  should  be  small  in  order  to 
prevent  the  tool  from  chattering  and  digging  into  the  work.  The 


FIG.  429. 


FIG.  430. 

angle  of  rake  y  should  be  as  great  as  the  hardness  of  the  metal 
operated  upon  will  permit. 

For  squaring  out  corners  a  tool  similar  to  the  diamond  point 
is  usually  used.  By  properly  indexing  the  rotating  table  spur  and 
internal  gear  may  be  cut  on  the  slotter,  using  a  cutter  of  the  cor- 
rect tooth  space  outline. 

The  key  seater  is  an  outgrowth  from  the  slotting  machine, 
and  although  designed  for  cutting  key  ways  only,  will,  when 
provided  with  suitable  attachments,  perform  various  classes  of 
slotting  machine  work.  A  standard  key  seater  is  shown  in  Fig. 
431.  A  cutter  bar  is  operated  by  a  crank  motion  in  the  base  of 
the  machine,  similar  to  the  drive  on  a  slotting  machine.  The 


THE    SLOTT1NC.    MACHINE    AND    KEY    SEATER.  309 

upper  end  of  the  bar  is  supported  by  a  suitable  overhanging  arm. 
The  work  table  upon  which  the  pulley  or  gear  to  be  key- waved 
is  supported  may  be  tilted  the  necessary  amount  to  give  the  re- 
quired taper  in  the  key  way,  and  is  also  capable  of  a  slight  in  and 


FIG.  431. 

out  motion,  independent  of  the  feed  which  advances  it  to  the  cut- 
ter. This  motion  is  necessary  in  order  to  clear  the  cutter  from 
•dragging  on  the  return  stroke. 

The  form  of  cutter  used  on  this  machine  is  shown  in  Fig.  432 


3io 


MODERN    MACHINE    SHOP    TOOLS. 


and  the  bar  in  which  it  is  held  in  Fig.  433.  These  cutters  are 
ground  from  the  bottom  only  and  should  be  kept  sharp.  The 
work  is  centered  to  the  bore  by  suitable  bushings.  The  feed  screw 
is  graduated  to  thousands  and  provided  with  a  stop  nut,  which 


FIG.  434. 


enables  any  number  of  bores  of  the  same  diameter  to  be  key- 
waved  to  the  same  depth. 

For  a  great  deal  of  special  work  a  cutter  bar  of  rectangular 
section  can  be  conveniently  used.  In, such  a  case  the  width  of  the 
cutter  should  exceed  the  thickness  of  the  bar  which  allows  the 


THE    SLOTTING    MACHINE    AXI)    KEY    SKATER.  3!  I 

cutter  to  work  out  square  corners.  For  the  cutting  of  external 
key-ways  in  short  shafts  and  spiders  the  key-seater  is  excellently 
adapted. 

For  the  key-seating  of  very  large,  heavy  work  portable  key- 
seaters  are  used.  In  Fig.  434  is  shown  a  Morton  portable  ma- 
chine operating  on  a  large  pulley.  These  tools  are  made  in  four 
sizes,  ranging  from  24  to  72  inch  stroke.  They  are  virtually 
draw  stroke  shapers  without  columns.  'They  are  operated  either 
by  a  rope  transmission  or  electrically,  a  motor  in  the  latter  case 
being  attached  directly  to  the  machine. 


CHAPTER   XXIII. 

MILLING  MACHINES. 

The  milling  machine  and  its  great  popularity  are  due  to  the 
peculiar  adaptability  of  the  rotating  cutter  to  the  machining  of 
plane  and  irregular  surfaces  on  such  a  wide  variety  of  work. 
The  variety  of  work  that  the  milling  machine  is  capable  of  per- 
forming is  much  greater  than  can  ordinarily  be  accomplished  on 
the  planer  or  shaper.  In  thoroughly  familiarizing  himself  with 
these  machines  the  mechanic  has  much  more  to  learn  as  to  set- 
tings and  manipulation  in  the  milling  machine  than  in  the  planer 
and  shaper.  With  the  latter  machines,  however,  more  skill  is 
required  in  the  manipulation  for  the  production  of  accurate  work 
than  with  the  former.  This  arises  from  the  fact  that  on  the 
planer  all  measurements  must  be  separately  made,  inasmuch  as 
the  cutting  tool  generates  the  profile  of  the  work  by  a  series  of 
parallel  cuts,  all  changes  in  plane  of  the  profile  requiring  sepa- 
rate adjustments  and  measurements.  With  the  milling  machine, 
however,  the  cutter  is  so  formed  as  to  generate  the  full  profile  of 
the  work  surface  as  the  cutter  advances,  setting  measurements 
alone  being  necessary.  With  the  planing  machines  the  accuracy 
of  the  work  depends  very  largely  upon  the  personal  skill  of  the 
operator,  while  with  the  milling  machine  the  accuracy  of  the 
cutting  tool  has  much  to  do  with  the  quality  of  the  work.  With 
the  milling  cutter  and  the  work  once  set,  the  accuracy  with 
which  a  certain  work-surface  profile  can  be  produced  upon  one 
or  more  pieces  depends  wholly  upon  the  wear  on  the  cutting 
edges  of  the  cutter.  As  the  cutters  are  usually  formed  with  a 
number  of  teeth,  the  work  is  divided  up  among  these  teeth,  re- 
ducing the  wear  upon  them.  This  is  not  only  because  each  unit 
of  length  of  each  tooth  performs  only  a  small  portion  of  the 
total  work  as  compared  with  the  cutting  edge  of  the  planer  tool 
of  unit's  length,  but  because  that  particular  portion  of  the  tooth 
is  performing  work  for  only  a  small  portion  of  each  revolution, 
thus  giving  it  an  opportunity  to  cool  and  recover  before  each 
time  it  comes  in  contact  with  the  work. 

The  advantage  of  the  milling  machine  over  the  planer  lies  very 
largely  in  its  ability  to  produce,  with  reasonable  accuracy,  a  large 


MILLING    MACHINKS.  313 

number  of  duplicate  surfaces,  the  formed  cutter  and  removal  of 
the  personal  error  in  the  making  of  measurements  by  the  oper- 
ator being  the  factors  that  enable  it  to  produce  these  results.  For 
the  producing  of  many  plane  surfaces,  and  especially  on  work 
that  is  not  to  be  duplicated,  the  milling  machine  possesses  no 
advantage  over  the  planer  and  shaper.  Its  advantages  for  certain 
classes  of  work,  however,  are  great,  as  illustrated,  for  example, 
in  Fig.  435.  This  shows  a  milling  gang  cutter  made  up  of  seven 
cutters  and  capable  of  producing  at  one  traverse  over  the  work  a 
profile  that,  if  produced  in  a  planer,  would  require  no  less  than 
eleven  separate  measurements,  aside  from  the  working  out  to  line 
of  the  curved  portion.  It  is  only  after  the  operator  has  become 
skilled  in  its  use  and  thoroughly  familiar  with  its  every  detail 
that  he  can  appreciate  the  great  capabilities  of  this  class  of  ma- 
chine tools. 

When  used  as  a  manufacturing  tool,  producing  large  numbers 


FIG.  435. 
• 

of  duplicate  parts,  the  results  obtained  from  the  use  of  the  milling 
machine  lies  almost  wholly  in  the  intelligent  selecting  of  proper 
cutters  and  fixtures  for  each  special  operation  and  when  once  set 
does  not  require  highly  skilled  labor  to  operate  it.  When  used  as 
a  jobbing  machine,  however,  the  operator  should  be  quick  and 
skillful  to  obtain  good  results. 

The  plain  and  universal  milling  machines  of  the  column  pat- 
tern are  most  extensively  used  for  general  shop  purposes.  In 
Fig.  436  is  shown  a  universal  machine  of  this  pattern.  The  col- 
umn and  knee  resemble  somewhat  the  same  parts  in  the  shaper. 
The  upper  portion  of  the  column  carries  the  spindle  and  cone, 
the  spindle  on  all  other  than  the  smallest  sizes  being  back-geared 
in  precisely  the  same  manner  as  on  the  lathe.  The  outer  end  of 
the  spindle  is  always  supported  by  a  suitable  overhanging  arm. 
The  work  table  is  adjustable  in  and  out  from  the  face  of  the 
column  and  vertically,  these  adjustments  being  made  by  screws 


314  MODERN    MACHINE    SHOP    TOOLS. 

with  operating  handles  conveniently  placed  and  moving  over 
dials  graduated  to  measure  the  amount  of  table  movement  in 
thousandths  of  an  inch.  The  knee  is  gibbed  to  the  face  of  the 
column  and,  in  the  universal  machine,  the  work  table  is  gibbed 
in  a  swing  frame  which  pivots  to  a  slider  which  in  turn  is  gibbed 
to  the  upper  face  of  the  knee.  Through  the  office  of  the  swing 
frame  the  table  can  be  set  at  an  angle  from  its  right-angle  posi- 
tion with  the  cutter  spindle.  In  some  machines  the  table  can 
be  carried  through  a  complete  revolution,  while  with  others 
the  range  is  limited.  The  table  is  provided  with  a  longitudinal 
feed  automatically  operated  in  either  direction.  An  automatic 


FIG.  436. 

in-and-out  and  up-and-down  feed  may  also  be  applied  when  de- 
sired. The  feed  mechanisms  are  so  designed  as  to  give  a  wide 
range  of  feeds.  The  universal  head,  to  be  described  hereafter,  may 
be  geared  with  the  longitudinal  feed  screw  for  the  cutting  of 
spirals.  The  plain  milling  machines  of  the  column  pattern  are 
similar  in  design  to  the  one  shown  in  Fig.  437.  In  this  type  of 
machine  the  work  table  is.  gibbed  directly  to  the  slider  and  its 
line  of  travel  restrained  entirely  to  one  at  right  angles  to  the 
spindle.  The  universal  head  and  tailstock  of  the  universal  type 
are  omitted,  plain  dividing  centers  usually  being  used  on  these 


MILLING    MACHINES. 


315 


machines.  The  work  table  is  somewhat  larger  on  the  plain  than 
on  like  sizes  of  the  universal  machine.  The  plain  machines  are 
preferable  for  plain  milling  work,  as  they  are  somewhat  more 
rigid  and  simpler  in  construction. 

For  tool  room  work  the  universal  column  pattern  machine 
stands  at  the  front.  As  probably  more  than  95  per  cent  of  the 
milling  work  outside  of  the  tool  room  is  plain  milling,  we  find  the 
plain  machine  much  in  favor  for  general  work.  Although  the 
column  pattern  is  generally  conceded  as  the  proper  style  of  design 
for  the  universal  machines,  such  is  not  always  the  case  for  plain 


437. 


machines,  inasmuch  as  a  great  part  of  the  plain  milling  runs  into 
larger  and  heavier  work.  We  therefore  find  plain  milling 
machines  built  along  entirely  different  lines,  especially  when  used 
for  the  plainest  and  heavier  classes  of  work.  In  Fig.  438  is 
shown  a  form  of  plain  machine  commonly  known  as  the  Lincoln 
pattern.  It  is  an  exceedingly  simple  form  of  machine,  yet  very 
efficient  on  certain  classes  of  work.  The  outboard  support,  for 
the  spindle,  together  with  the  form  of  the  bed,  makes  a  rigid  ma- 
chine. The  driving  cone  is  mounted  on  the  bask  side  of  the  main 


MODERN    MACHINE    SHOP    TOOLS, 


FIG.  438. 


FIG.  4.39- 


M I LLI X G    M  AC  H I X  ES. 


.317 


upright,  driving  the  spindle  through  a  pinion  and  gear  connec- 
tion. As  the  vertical  adjustment  is  in  the  spindle  itself  instead  of 
in  the  work  table,  a  suitable  tightener  is  employed  for  keeping  the 
belt  tensions  correct  for  all  positions  of  the  spindle.  The  work 
table  is  given  the  usual  automatic  feed  under  the  spindle  and 
suitable  lateral  hand  adjustment.  In  Fig.  439  is  shown  a  form 
of  plain  milling  machines  somewhat  similar  in  appearance  to  the 
one  shown  in  Fig.  438.  The  design,  however,  provides  for  a 


FIG.  440. 

larger  work  table  and  the  machine  shown  has  two  heads,  making 
what  is  usually  termed  a  duplex  miller.  Machines  of  this  class 
are  well  suited  not  only  to  the  use  of  plain  or  axial  cutters,  but 
to  the  radial  or  end  cutter.  Thus  on  the  double-head  machine  of 
Fig.  439  two  radial  cutters  may  be  used  at  the  same  time  on  oppo- 
site sides  of  work  secured  to  the  table ;  or  one  axial  cutter  can  ma- 
chine the  upper  surface  while  a  radial  is  working  on  the  side. 
Fig.  440  illustrates  what  is  known  as  a  slabbing  milling  ma- 


MODERN    MACHINE    SHOP    TOOLS. 

chine.  It  resembles  in  appearance  a  planer,  is  a  massive,  power- 
ful machine,  and  in  the  form  shown  carries  a  large  slabbing 
cutter  for  removing,  heavy  cuts  at  coarse  feeds  from  the  work. 
These  machines  are  also  provided  with  horizontal  spindles  which 
can  be  operated  with  or  independently  of  the  vertical  spindles. 
In  this  case  the  horizontal  spindle  bearings  are  carried  on  the 
front  faces  of  the  housings.  The  vertical  spindles  usually  carry 


FIG.  441. 


radial  mills.  The  advantage  of  the  radial  mill  over  the  axial 
cutter  lies  in  the  fact  that  in  forcing  it  to  its  cut  the  pressure  is 
mostly  in  the  direction  of  the  line  of  the  feed  and  not  at  right 
angles  to  the  surface  being  machined,  thus  overcoming  most  of 
the  springing  in  the  work  that  occurs  or  tends  to  occur  in  the  use 
of  the  axial  cutter.  The  radial  cutter,  however,  does  not  leave  as 
smooth  a  surface  as  the  axial,  but  this  disadvantage  is,  on  a  great 


MILLIXC,    MACHINES. 


319 


deal  of  work,  more  than  overbalanced  by  the  greater  accuracy 
obtained. 

In  Fig.  441  is  shown  a  well-known  vertical  milling  machine 
intended  for  such  general  work  as  can  be  more  advantageously 
performed  by  a  cutter  operated  in  a  vertical  spindle  than  by  one 
on  the  horizontal  spindle  pattern  machines.  This  machine  in 
many  respects  resembles  the  regular  column  pattern  machines 
with  the  column  carried  upward  and  out  over  the  table  an 
amount  sufficient  to  bring  the  spindle  into  the  vertical  position. 


FIG.  442. 

The  vertical  spindle  brings  the  cutter  more  directly  under  the 
sight  and  control  of  the  operator  than  when  cutters  of  the  radial 
class  are  used  in  the  horizontal  spindle  machines.  This  type  of 
machine  also  has  the  advantage  of  a  circular  feed  by  which  a 
circular  table,  upon  which  work  is  placed,  may  be  given  a  rotary 
motion.  Thus  a  class  of  work  may  be  performed  that  would 
otherwise  require  the  use  of  formed  tools  in  the  lathe,  and  it 
can  be  done  more  quickly  than  in  the  lathe. 

Another  form  of  vertical  spindle  milling  machine  is  shown  in 
Fig.    442.      This    machine   is    designed    for    longer   and    heavier 


320 


MODKRX     MACHINE    SHOP    TOOLS. 


work  than  the  one  last  mentioned.  The  spindles  are  carried  on 
a  radial  arm,  thus  providing  a  cross  adjustment  to  the  spindle 
rather  than  the  table. 

In  Fig.  443  is  shown  a  pattern  of  vertical  milling  machine, 
more  commonly  known  as  a  die  sinking  machine  and  used  for 


PIG.  443. 

recessing  of  circular  or  irregular  shapes,  as  dies  for  drop  presses. 
The  work  to  be  operated  upon  is  held  in  a  vise,  which  may  be 
moved  in  all  directions  by  means  of  compound  table  slides.  The 
knee  is  adjusted  vertically  by  the  screw  and  large  hand  wheel 
shown.  Cutters  of  small  diameter  are  used  and  the  belted 


MILLIXr,    M. YC1I  INKS.  321 

spindle  drive  gives  a  smooth  steady  motion  to  the  cutter.  Where 
a  number  of  similar  pieces  are  to  be  operated  upon  a  pattern 
is  usually  used  for  guiding  the  work  to  the  cutter. 

For  the  milling  of  very  light  pieces,  as  sewing  machine  or 
gun  parts,  for  example,  a  light  lever  feed  machine  is  much  more 
convenient  than  the  heavier  pattern  tools.  The  speeds  are  bet- 
ter adapted  for  the  small  diameter  of  cutters  used  and  the  quick 
table  movement  makes  it  possible  to  turn  work  out  very  rapidly. 
A  machine  of  this  character  is  shown  in  Fig.  444. 

The  feed  mechanism  differs  quite  widely  on  machines  by 
different  builders  up  to  the  point  of  the  connection  with  the 
work  table.  At  this  point  one  of  two  systems  is  invariably  used 
—the  screw  or  the  rack  feed.  With  only  a  few  exceptions  the 
screw  feed  is  used  on  the  plain  and  universal  machines  of  the 
column  pattern.  On  the  heavy  slabbing  and  duplex  machines 
the  rack  feed  is  usually  employ- 
ed. The  rack  feed  furnishes  the 
best  form  for  a  quick  movement 
of  the  table,  but  possesses  the 
disadvantage  of  allowing  the 
table  and  work  to  draw  under 
the  cutter  in  cases  of  accident  or 
carelessness  on  the  part  of  the 
operator.  With  the  screw  feed 
the  table  can  be  moved  only  by 

the  rotating  of  the   screw.       A  FIG.  444. 

quick-geared  return  to  the  table 
is  usually  applied  to  the  screw-feed  machines. 

The  work  table  is  provided  with  T-slots  for  holding  the 
clamping  bolts  and  fixtures.  The  table  is  gibbed  to  the  bed 
to  prevent  lifting  and  usually  moves  in  flat  or  angular  guides. 
The  overhanging  arm  is  usually  made  of  the  style  shown  in  Fig. 
436,  which  enables  it  to  be  used  to  receive  and  support  the  several 
special  attachments  made  to  be  used  in  connection  with  ma- 
chines of  the  column  pattern.  Suitable  ties  are  now  furnished 
with  most  makes  of  milling  machines  connecting  the  outer  end 
of  the  overhanging  arm  with  the  knee,  which  adds  much  to  the 
rigidity  of  the  table  and  spindle  when  heavy  cuts  are  being 
taken. 

A  comparatively  wide  range  of  feeds  to  the  table  of  the 
milling  machine  is  considered  quite  important  and  especially 


322  MODERN    MACHINE    SHOP    TOOLS. 

so  on  the  back-geared  machines  where  the  variation  of  the  size 
and  speed  of  cutters  is  considerable.  This  range  of  feed  is 
usually  accomplished  by  means  of  stepped  pulleys,  gearing,  or 
a  combination  of  the  two.  Thus  a  pair  of  four-step  pulleys  will 
give  four  changes  of  speed  and  if  these  pulleys  are  of  different 
sizes,  by  transposing  them  on  their  spindles  four  more  changes 
may  be  obtained. 

The  power  of  the  feed  mechanism  must  be  sufficient  to  pull 
the  feeds  under  all  conditions,  and  convenient  in  changing  from 
one  rate  of  feed  to  another.  The  importance  of  being  able  to 
make  quick  changes  may  be  illustrated  in  the  case  of  large  cfia- 
meter  end  or  radial  milling  cutters  operating  upon  wide  work. 
The  rate  of  feed  on  entering  and  leaving  the  work  can  be  ma- 
terially greater  than  when  the  cut  is  operating  on  the  full  width 
of  the  work.  If  the  cuts  are  comparatively  short  the  time  saved 
by  entering  and  leaving  the  work  on  quicker  feed  is  of  material 
importance. 

On  machines  other  than  the  smaller  sizes,  automatic  in  and 
out  and  vertical  power  feeds  are  usually  provided. 

The  all-gear  feed  mechanism  used  on  the  Cincinnati  milling 
machines  is  shown  in  detail  in  Figs.  445  A  and  B  and  446  A 
and  B.  By  means  of  the  sliding  gear  in  the  upper  gear  box, 
two  changes  of  speed  are  given  to  the  vertical  shaft  for  each 
speed  of  the  spindle.  The  vertical  shaft  through  the  pair  of 
lower  bevel  gears  drives  the  two  feed  gears  which  in  turn  drive 
the  two  feed  cones  which  run  loose  and  independent  of  each 
other  on  their  shaft.  The  large  feed  gear  meshes  with  the  small 
gear  on  one  cone  and  the  small  gear  meshes  with  the  large  gear 
on  the  other  cone. 

The  intermediate  gear  by  means  of  a  suitable  mechanism 
may  be  made  to  gear  with  any  one  of  the  cone  gears,  thus  giv- 
ing a  wide  range  of  feed  changes.  In  changing  feeds  the  upper 
lever,  446  A,  is  placed  in  the  extreme  left-hand  position.  This 
throws  the  intermediate  gear,  Fig.  446  B,  back  an  amount  suf- 
ficient to  clear  the  cone  gears.  By  placing  the  lower  lever  in 
position  indicated  for  the  desired  feed,  the  intermediate  gear 
will  be  placed  opposite  the  proper  gear  on  the  cone. 

Moving  the  upper  lever  to  the  right  engages  the  gears.  The 
variations  in  the  rate  of  feed  obtained  give  nearly  a  uniform 
progression. 

The  dividing  or  universal  head  is  the  part  of  the  universal 


MILLING    MACHINES. 


323 


machine  with  which  the  beginner  usually  has  the  most  trouble 
in  familiarizing-  himself.  A  dividing  or  indexing  head  in  its 
simple  form,  and  as  usually  used  on  the  plain  milling  machine, 
is  shown  in  Fig.  447.  With  the  tailstock  shown  it  comprises 
what  is  commonly  known  as  a  pair  of  index  centers.  Suitable 
lugs  on  the  bottom  fit  neatly  in  the  neck  of  the  T  slots  in  the 
work  table,  thus  preserving  the  alignment  of  head  and  tail  spin- 
•dles.  The  head  spindle  is  capable  of  rotation  only.  It  carries 


FIG.  44 5 A. 


Spindle  ofMacliio* 


FIG.  4453. 


MODERN    MACHINE    SHOP    TOOLS. 


a  worm  gear  which  is  operated  by  the  worm  and  crank  shown. 
The  ratio  between  worm  and  gear  is,  on  all  indexing  heads, 
one  to  forty.  In  the  one  illustrated  there  are  80  teeth  in  the 
gear  and  a  double  thread  on  the  worm.  It  is  therefore  neces- 
sary to  make  40  turns  of  the  crank  and  worm  to  make  one  turn 


FIG.  446A. 


FIG.  446B. 


MILLING    MACHINES.  325 

of  the  gear  and  spindle.  The  crank  moves  over  a  carefully- 
divided  dial  which  is  secured  to  the  head.  A  small  pin,  ad- 
justable radially  in  the  crank,  may  be  set  to  engage  in  the  .holes 
of  any  of  the  circles.  As  it  is  not  desirable  to  have  the  index 
plates  too  large  in  diameter  or  the  holes  too  small,  several 
plates  are  necessary  in  order  to  get  the  range  of  divisions  us- 
ually required.  \Yith  the  one  shown  three  plates  are  finished, 
making  all  divisions  up  to  50,  all  even  divisions  to  100,  with 
many  of  the  uneven  divisions  between  50  and  100,  and  many 
even  and  uneven  divisions  above  100.  The  sector  serves  to 
assist  in  counting  the  number  of  spaces  between  the  holes  and 
can  be  adjusted  to  include  any  desired  number  of  spaces  between 
its  two  radial  arms. 

As   much   of  the   miscellaneous   dividing   work   done   on   an 


FIG.   447. 

index  head  is  for  2,  3,  4,  6,  8,  12  and  24  parts,  a  more  rapid 
means  of  obtaining  these  divisions  than  by  turning  the  worm 
is  frequently  applied.  In  the  centers  shown,  there  are  24  holes, 
equally  spaced,  in  the  face  of  the  worm  gear,  with  a  substantial 
pin  arranged  to  engage  in  them.  When  dividing  by  these  holes 
the  worm  is  dropped  out  of  mesh  with  the  gear. 

The  universal  head  is  a  more  complicated  piece  of  mechan- 
ism. In  Fig.  448  are  shown  side  and  end  sectional  views  of  the 
Brown  &  Sharpe  universal  dividing  head.  A  side  view  is  shown 
in  Fig.  449.  The  worm  gear  B  is  attached  to  the  spindle,-  and  a 
side  shaft  carries  the  worm  A. 

The  spindle  head  is  mounted  in  a  suitable  housing  and  can 
be  elevated  through  an  angle  of  90  degrees  and  firmly  clamped 
in  any  position.  The  spindle  may  also  be  depressed  through  a 
few  degrees.  The  universal  head,  as  made  by  some  builders  is 
capable  of  spindle  settings  at  any  angle  within  o  and  180  degrees. 

\\  hen  used  for  plain  indexing  the  worm  can  be  disengaged 


326 


MODERN    MACHINE    SHOP    TOOLS. 


from  the  spindle  gear  and  the  required  division  obtained  by 
means  of  the  index  plate  C,  which  is  locked  in  position  by  the 
pin  D.  As  only  a  limited  number  of  divisions  can  conveniently 


FIG.  448. 


FIG.  449. 

be  obtained  in  this  way,  the  usual  method  is  by  means  of  the 
regular  index  plate  I. 

The  crank  J  is  secured  to  the  worm  shaft,  and  the  sector  S  is- 


MILLING    MACHINES. 


327 


held  by  a  spring  between  the  dividing  plate  and  the  crank  \vitfi 
just  enough  friction  to  keep  it  in  position  when  set. 

The  sleeve  to  which  the  index  plate  I  is  secured,  carries  a 
gear  on  its  inner  end  which  meshes  with  another  gear  on  the 
axis  R  and  about  which  the  head  rotates  in  setting  to  different 
angles.  This  latter  gear  meshes  with  a  third  gear  on  the  same 
axis  and  secured  to  the  upper  of  a  pair  of  spiral  gears,  which 
transmit  the  motion  from  the  train  of  gears  leading  from  the 
table  feed  screw.  A  post  may  be  drawn  out  from  the  head  and 
caused  to  engage  in  a  suitable  notch  in  the  back  of  the  plate,  or, 
in  cases  where  the  holes  are  drilled  through  the  plate,  in  one  of 


FIG.  45 1. 


FIG.  452. 


the  holes.  This  secures  the  dividing  plate  from  rotation  and  divi- 
sions on  the  spindle  are  obtained  in  the  same  manner  as  described 
above.  When  it  is  required  to  rotate  the  spindle  while  the  work  is 
being  operated  upon  by  the  cutter,  as  is  the  case  in  the  cutting  of 
spirals,  a  geared  combination  between  the  worm  spindle  and  the 
table  feed  mechanism  becomes  necessary. 

The  milling  machine  is  capable  of  receiving  a  large  variety  of 
attachments  for  performing  special  operations,  or  regular  opera- 
tions with  greater  facility  than  can  be  had  with  the  machine  in 
its  standard  form. 

The  vise  is  a  regular  attachment  on  all  universal  machines 


328  MODERN    MACHINE    SHOP   TOOLS. 

and  plain  machines  of  the  column  pattern.  It  is  of  two  standard 
forms;  plain,  as  shown  in  Fig.  450,  and  swivel  as  shown  in  Fig. 
451.  The  plain  vise  is  provided  with  tongues  to  fit  the  wards  in 
the  work  table  and  can  be  readily  set  with  the  jaws  parallel  with 
or  at  right  angles  to  the  spindle.  It  cannot,  however,  be  con- 
veniently set  at  any  other  angle.  The  swivel  vise  has  a  gradu- 
ated base  resting  on  a  plate  which  is  tongued  and  bolted  to  the 
wards  in  the  table.  The  swivel  vise  is  very  convenient  for  angu- 
lar milling.'  A  special  tilting  vise  shown  in  Fig.  452  is,  with  its 
tilting  jaws  and  swivel  base,  well  adapted  to  the  milling  of  a 
large  variety  of  angular  surfaces.  In  all  milling  machine  vises 
the  movable  jaw  is  accurately  fitted  and  gibbed  to  the  body,  and 
the  jaw  faces,  which  are  usually  made  of  soft  steel,  are  secured 
to  the  jaws  by  means  of  screws.  The  surface  of  the  jaw  faces 
should  be  kept  true  and  smooth,  as  they  will  then  hold  finished 
work  surfaces  true  for  the  cut  and  without  injury  to  the  work. 
Extra  jaw  faces  hardened  and  with  roughed  surfaces  may  be 
used  for  holding  forgings,  castings  and  rough  work.  For  the 
holding  of  special  and  irregular  work  special  formed  jaw  faces 
may  be  substituted  for  the  regular  ones. 

As  the  universal  dividing  head  is  a  part  of  the  universal 
milling  machine,  it  is  not  considered  as  an  attachment.  The 
plain  index  head  already  described  under  Fig.  447,  however,  is 
strictly  a  milling  machine  attachment.  A  first-class,  three- 
jawed  universal  chuck  fitted  to  the  spindle  of  the  index  head  is  a 
very  necessary  accessory  to  the  machine,  as  much  of  the  work- 
to  be  operated  upon  can  or  must  be  held  in  the  chuck. 

The  vertical  spindle  milling  head  shown  in  Fig.  453,  when  ap- 
plied to  the  plain  or  universal  machines,  converts  them  into  verti- 
cal spindle  machines.  These  heads  are  supported  on  the  overhang- 
ing arm,  and  the  nose  of  the  spindle  bearing.  The  vertical 
spindle  is  driven  from  the  main  spindle  by  bevel  gears.  A 
graduated  index  enables  it  to  be  set  at  any  desired  angle  from 
the  vertical,  thus  making  it  possible  to  mill  many  angular  sur- 
faces with  a  plain  end  or  shank  milling  cutter.  These  attach- 
ments are  very  convenient  for  the  cutting  of  T-slots,  key  seating 
and  profiling,  as  well  as  angular  work.  Another  attachment, 
termed  a  universal  milling  attachment,  is  shown  in  Fig.  454. 
This  has  in  addition  to  the  vertical  spindle  an  auxiliary  one  at 
right  angles  to  it  and  driven  from  it  by  means  of  spiral  gears. 
With  this  auxiliary  spindle  set  parallel  with  the  surface  of  the 


MILLING    MACHINES. 


329 


FIG.  453. 


330  MODERN    MACHINE    SHOP    TOOLS. 

work  table  and  its  line  of  travel,  it  makes  a  convenient  rack  cut- 
ting attachment.  In  connection  with  the  spiral  head  on  the  uni- 
versal machines,  it  can  be  used  to  advantage  in  cutting  spirals  of 
large  spiral  angle,  as  the  axis  of  the  cutter  can  be  set  to  the 
spiral  angle  instead  of  the  work  table.  The  auxiliary  spindle 
can  readily  be  removed  when  not-  in  use,  leaving  a  simple  vertical 
milling  attachment.  Attachments  of  this  class  become  of  special 
value  in  shops  when  the  amount  of  work  that  can  be  advantage- 
ously done  by  vertical  milling  does  not  warrant  putting  in  a  verti- 
cal milling  machine. 

In  Fig.  455  is  shown  a  circular  milling  attachment.  It  con- 
sists of  a  circular  plate  gibbed  to  a  round  base  and  provided  with 
a  worm  gear  into  which  the  feed  worm  meshes.  The  base  clamps 
to  the  table  of  the  milling  machine  and  the  work  is  secured  to 


FIG.  455- 

the  top  of  the  circular  table,  suitable  T-slots  being  provided  for 
the  clamp  bolts.  This  attachment  is  of  special  value  on  the  verti- 
cal milling  machines  and  in  connection  with  the  vertical  milling 
attachments  on  the  column  pattern  plain  and  universal  machines. 
It  may  be  provided  with  an  automatic  feed,  which  increases 
materially  its  usefulness  where  a  considerable  amount  of  work 
is  to  be  done  on  it.  This  attachment  can,  when  the  table  is  suit- 
ably gibbed  to  the  base,  be  clamped  to  a  substantial  right  angle 
knee  plate  and  the  faces  and  periphery  of  work,  as  gear  blanks, 
pulleys,  etc.,  successfully  milled  with  cutters  on  the  main  spindle 
of  the  machine.  For  this  class  of  work  an  attachment  similar  to 
the  one  shown  in  Fig.  456  is  best  adapted.  The  construction  of 
this  attachment  is  evident.  As  shown,  it  is  arranged  to  carry  two 
blanks  to  be  operated  upon  at  the  same  time,  the  rims  being  com- 
pletely finished  at  one  rotation  of  the  work. 


MILLING    MACHINES. 


331 


It  is  frequently  desirable  to  use  cutters  of  small  diameter  and 
requiring  high  rotative  speed  in  the  larger  sizes  of  milling  ma- 
chines. As  the  spindle  speeds  are  altogether  too  slow  for  this 


FIG.  456. 


FIG.  457- 

purpose,  high  speed  milling  attachments,  one  of  which  is  shown 
in  Fig.  457,  are  provided. 

The  attachment  consists  of  a  frame  which  fits  the  front  face 
of  the  column  and  carries  a  light  spindle  for  receiving  the  small 
cutters  used.  On  the  inner  end  of  this  spindle  is  a  small  pinion 


332  MODERN     MACHINE    SHOP    TOOLS. 

which  meshes  wi£h  an  internal  gear  screwed  on  the  nose  of  the 
main  spindle. 

A  rack-cutting  attachment  is  shown  in  Fig.  458.  A  device 
similar  to  this  is  necessary  when  racks  of  any  considerable  length 
are  to  be  cut  on  a  milling  machine,  as  the  motion  of  the  table  in 
line  with  the  spindle  is  not  great,  and  the  distance  the  cutter  can 
be  set  from  the  nose  of  the  spindle  is  also  small.  With  the  at- 
tachment shown,  the  length  of  the  rack  section  that  can  be  cut 
at  one  setting  is  limited  by  the  longitudinal  travel  of  the  table. 
In  the  device  shown,  the  frame  is  securely  attached  to  the  front 
face  of  the  column,  and  the  cutter  spindle  driven  by  a  suitable 
chain  of  gears.  The  rack  blank  is  clamped  in  the  special  vise 


FIG.  458. 

shown,  and  the  depth  and  settings  for  each  cut  are  obtained  by 
means  of  the  graduated  dials  on  elevating  and  longitudinal 
screws.  The  feed  is  in  and  out  by  hand,  or  automatically,  if  the 
machine  is  provided  with  automatic  lateral  feeds. 

The  spiral  cutting  attachment  shown  in  Fig.  459  is  adapted,  in 
connection  with  the  plain  milling  machine,  to  the  cutting  of 
spirals.  It  frequently  happens  that  the  amount  of  spiral  milling 
to  be  done  in  a  shop  would  not  warrant  putting  in  a  universal 
machine,  and  in  such  cases  the  attachment  shown  serves  its  pur- 
pose admirably.  It  consists  of  a  circular  base,  carrying  a  suitable 
frame  in  which  a  work  table  is  gibbed.  The  frame  is  preferably 
detachable  from  the  base,  graduated  and  capable  of  being  clamped 
at  any  desired  angle  with  the  spindle  of  the  machine.  The  work 
table  carries  a  head  and  tail  stock  for  supporting  the  work.  The 


MILLING    MACHINES. 


333 


head  stock  spindle  carries  at  its  outer  end  a  bevel  gear  which 
revolves  upon  it.  The  rear  face  of  the  bevel  gear  is  provided 
with  circles  of  drilled  holes,  similar  to  an  index  plate.  A  radial 
arm  keyed  to  the  spindle  carries  a  pin  which  engages  in  the  holes 
of  the  plate  and  through  which  the  drive  is  carried  from  the 


FIG.  459. 

gears  to  the  spindle.  The  balance  of  the  gear  combination  is  a 
suitable  system  of  change  gears  substantially  as  described  in  con- 
nection with  the  universal  dividing  head.  A  worm  feed  operated 
by  hand  is  usually  provided  on  attachments  of  this  class. 

An   attachment    for   the   cutting   of   cams   is   shown    in    Fig. 


MILLING  MACHINE 
SPINDLE 


FIG.  460. 

460.  It  consists  of  a  base  plate  A,  which  can  be  bolted  to 
the  work  table  of  the  milling  machine,  and  a  head  stock  which 
is  mounted  on  the  slide  C.  C  is  gibbed  to  slide  in  the  base 
plate.  The  head  stock  carries  a  spindle  with  a  worm  gear 
G  on  its  outer  end.  The  worm  S  engages  the  gear  and  the  spin- 
dle is  given  a  slow  feed  rotation  by  the  pulley  P  or  a  crank  which 


334 


MODERN    MACHINE    SHOP    TOOLS. 


can  be  substituted  in  its  place  when  power  feed  is  not  available. 
R  is  a  small  roller  mounted  on  a  suitable  support  which  extends 
upward  from  the  base  plate.  The  master  cam  F,  which  is  of  the 
same  contour  as  the  required  cam,  is  mounted  on  the  spindle,  as 
is  also  the  work.  The  work  table  of  the  milling  machine  is  ad- 
justed vertically  and  laterally  so  as  to  bring  the  center  of  the 
roller  R  and  the  milling  cutter  in  the  same  axial  line.  A  weight 
W  connected  by  a  rope,  over  a  sheave  at  the  end  of  the  table, 
with  the  slide  C,  holds  the  master  cam  constantly  in  contact  with 
the  roller  as  the  spindle  and  work  are  rotated.  The  master  cam 
is  usually  of  the  exact  size  of  the  required  cam,  and  in  that  case, 
the  roller  R  should  be  of  the  same  diameter  as  the  milling  cut- 
ter. If  the  master  cam  is  larger  or  smaller  than  the  required 


FIG.  461. 

cam,  the  diameter  of  the  roller,  for  the  same  diameter  of  the 
cutter,  must  be  decreased  or  increased  as  the  case  may  be,  in 
order  that  the  sum  of  the  master  cam  and  the  roller  radii  will 
at  all  points  equal  the  sum  of  the  required  cam  and  the  cutter 
radii.  For  the  cutting  of  cylindrical  cams  the  spindle  must  stand 
at  right  angles  with  the  cutter  spindle.  The  attachment  is  so 
constructed  that  the  spindle  head  can  readily  be  secured  in  such  a 
position  on  the  slide  plate  C. 

An  oil  pump  for  supplying  a  lubricant  to  the  cutter  and  work 
when  milling  steel  can  properly  come  under  the  head  of  attach- 
ments. In  Fig.  461  is  shown  such  a  pump.  It  is  attached  to  a 
suitable  reservoir  and  driven  from  an  independent  countershaft. 

In  Fig.  462  is  shown  a  slotting  attachment  for  the  milling 
machine.  The  guide  casting  is  secured  to  the  overhanging  arm 


MILLING    MACHINES. 


335 


at  its  upper  end,  and  at  the  lower  end  is  clamped  to  a  yoke  casting 
which  is  secured  to  the  front  face  of  the  column.  The  guide  may 
be  set  at  any  angle  between  o  and  10  degrees  either  side  of  the 
center  line.  Motion  is  given  the  slide  by  a  crank  screwed  on  the 
nose  of  the  spindle.  The  stroke  of  the  slide  can  be  adjusted  to 
.any  required  length  between  o  and  2  inches.  The  tools,  which 


FIG.  462. 


are  provided  with  ^i -inch  round  shanks,  are  firmly  clamped  in 
position.  In  the  use  of  the  attachment  both  the  longitudinal  and 
transverse  table  feeds  are  available  and  by  means  of  the  gradu- 
ated dials  very  accurate  readings  can  be  made.  This  attachment 
is  specially  valuable  in  the  forming  of  special  tools,  jigs,  dies  and 
templates. 


CHAPTER    XXIV. 

MILLING    MACHINE    CUTTERS. 

The  milling  of  metallic  surfaces  requires  a  rotating  cutter  pro- 
vided with  one  or  more  teeth  having  an  edge  and  temper  suited 
to  the  nature  of  the  material  operated  upon.  As  to  construction, 
milling  cutters  may  be  divided  into  the  two  classes — solid  and 
inserted  tooth.  All  small  and  most  of  the  medium-sized  cutters 
may  be  brought  under  the  first  class,  as  they  are  made  from  a 
single  piece  of  tool  steel;  but  when  the  dimensions  become  large 
the  cost  of  the  steel  is  an  important  point,  which,  together  with 
the  risks  incident  to  the  proper  hardening  of  such  large  masses 
of  tool  steel,  warrants  the  greater  expenditure  of  labor  usually 
necessary  in  the  making  of  inserted  tooth  cutters.  The  inserted 
tooth  cutter  has  only  teeth  of  tool  steel,  the  core  or  body  being 
of  cast  iron  or  mild  steel. 

As  to  classification,  milling  cutters  naturally  fall  under  four 
heads,  as  determined  by  the  four  distinct  varieties  of  work  per- 
formed, as  follows  :  Axial — those  cutters  used  for  .milling  plain 
surfaces  which  are  parallel  to  the  axis  of  rotation  of  the  cutter ; 
Radial — those  which  will  mill  plane  surfaces  at  right  angles  to 
the  axis ;  Angular — those  used  in  milling  plane  surfaces  at  any 
angle  other  than  90  degrees  with  the  axis ;  and  Form  cutters, 
used  for  machining  all  curved  or  irregular  surfaces. 

In  Fig.  463  A  is  shown  an  axial  or  plain  milling  cutter,  as  it  is 
usually  called.  It  has  teeth  on  the  cylindrical  surface  only,  which, 
when  the  cutter  exceeds  about  one-half  inch  in  thickness,  are 
cut  spirally,  as  shown  in  the  figure.  When  these  cutters  are 
less  than  three-sixteenths  of  an  inch  in  thickness,  they  are  called 
metal  slitting  saws,  and  the  sides  are  ground  slightly  dishing, 
which  serves  to  give  the  teeth  clearance  in  the  grooves  they  cut. 
This  is  of  much  importance  when  the  cut  is  deep,  as  is  frequently 
the  case  when  using  the  metal  slitting  saw. 

The  spiral  teeth  on  these  cutters  are  necessary  for  the  follow- 
ing reasons.  If  the  teeth  are  straight,  each  tooth  as  it  comes 
into  action  would  strike  square  against  the  work,  producing  a 
shock  and  consequent  springing  of  work  and  cutter  arbor ;  and 
as  each  tooth  leaves  the  work  the  sudden  release  of  pressure 


MILLING    MACHINE    CUTTERS. 


337 


causes  reverse  spring.  If  the  cut  is  not  deep,  and  only  one  or 
two  teeth  cutting  at  a  time  this  effect  will  be  more  marked  than 
when  a  greater  number  of  teeth  are  in  action,  and  the  effect  of 
the  spring  will  be  clearly  shown  by  the  waved  and  uneven  condi- 
tion of  the  surface  produced.  If,  on  the  other  hand,  the  teeth  are 
arranged  spirally  they  will  come  into  and  leave  the  work  gradu- 
ally, thus  avoiding  shock  and,  what  is  very  important,  give  a 
shearing  cut. 

Plain  milling  cutters  with  nicked  teeth,  an  example  of  which 


FIG.  463A. 


FIG.  4638. 


is  shown  in  Fig.  463  B,  are  especially  adapted  for  heavy  milling. 
The  breaking  up  of  the  chip  by  the  nicked  tooth  makes  possible  a 
very  much  heavier  cut  than  can  be  taken  with  the  ordinary  form 
of  continuous  tooth. 

When  provided  with  teeth  on  their  faces,  these  cutters  become 
\vhat  are  called  radial,  face,  side  or  straddle  mills.     When  the 


FIG.   464. 


FIG.  465. 


teeth  are  on  but  one  face  and  the  cutters  used  for  straddle  work, 
they  must  be  cut  right  and  left,  as  otherwise  one  cutter  would  run 
backward.  The  cutter  shown  in  Fig.  464  can  be  run  in  either 
direction,  as  it  has  teeth  on  both  faces,  and  constitutes  the  form 
usually  used.  These  cutters,  when  worked  in  pairs,  and  espe- 
cially for  shoulder  work,  as  shown  in  Fig.  465,  should  be  care- 
fully ground  to  the  same  diameter. 


338 


MODERN    MACHINE    SHOP    TOOLS. 


The  end  or  shank  milling  cutter  shown  in  Fig.  466  is  virtual- 
ly a  radial  mill  of  small  diameter  provided  with  its  own  inde- 
pendent shank.  These  cutters  are  seldom  made  larger  than  il/2 
inches  in  diameter.  Their  form  permits  the  small  diameters, 
which  are  so  necessary  in  much  of  the  fine  milling  work.  These 
cutters  are  made  right  and  left  handed,  and  frequently  the  teeth 
on  the  circumference  are  cut  spirally,  as  shown,  straight  teeth, 
however,  being  most  used.  The  advantage  of  the  spiral  tooth  for 
the  end  mill  when  used  as  an  axial  cutter  arises  from  the  de- 


FIG.  466. 

creased  shock  and  vibration  due  to  the  steady  shearing  cut, 
which  reduces  the  tendency  of  the  tool  to  jar  loose  in  the  spin- 
dle or  collet  bearing.  The  direction  of  the  spiral  must  be  such 
that  the  end  thrust  of  the  cutting  pressure  tends  to  force  the 
shank  into,  rather  than  draw  it  out,  of  its  bearing.  In  a  right- 
hand  mill  the  angle  of  the  spiral  would  be  left-handed. 

If  it  is  desired  to  mill  a  slot  with  the  end  of  the  shank  cutter, 
shown  in  Fig.  466,  which  does  not  start  at  the  edge  of  the  work, 
a  hole  must  be  drilled  into  the  work  of  a  diameter  at  least  equal 


FIG.  467. 

to  the  diameter  of  the  space  without  teeth  in  the  end  of  the  cutter, 
as  otherwise  the  cutter  could  be  made  to  enter  only  a  depth 
equal  to  the  depth  of  this  space,  and  could  not  then  be  moved 
along  the  work.  A  form  of  cutter  shown  in  Fig.  467  overcomes 
this  difficulty,  as  the  inner  ends  of  the  radial  teeth  are  provided 
with  cutting  edges,  which  enables  them  to  cut  their  way  out  when 
moved  along  the  work.  The  length  of  these  cutting  edges  limits, 
however,  the  depth  to  which  the  cutter  may  be  made  to  enter 
the  work  at  any  one  setting.  In  this  form  of  cutter  a  smaller 
number  of  teeth  must  be  used.  The  end  mill  may  be  placed 


MILLING    MACHINE    CUTTERS. 


339- 


under  either  of  the  two  first  classes,  as  it  may  be  used  for  ma- 
chining surfaces  which  are  either  parallel  with  or  at  right  angles 
to  the  axis  of  rotation. 

The  standard  T-slot  cutter  is 'shown  in  Fig.  468.  This  tool  is 
used  in  cutting  the  slots,  a  section  of  which  is  shown  in  Fig.  469, 
the  central  portion  of  the  slot  having  been  previously  removed. 
In  the  cutter  shown,  alternate  teeth  cut  on  the  inner  and  outer 
edges.  These  face  teeth,  however,  have  little  work  to  do,  and  are 


FIG.  468. 

on  some  cutters  omitted,  the  faces  being  ground  slightly  dishing, 
to  provide  the  necessary  clearance.  T-slot  cutters  are  made  1-32 
of  an  inch  over  size  in  diameter,  to  allow  for  grinding.  They 
are  usually  made  left-hand,  as  shown  in  the  figure. 

In  Fig.  470  is  showrn  an  angular  cutter.  These  cutters  are  us- 
ually provided  with  face  teeth,  as  shown  in  the  figure.  For 
straight  work  the  face  teeth  may  be  omitted,  the  face  being 
ground  slightly  concave.  When  the  character  of  the  work  re- 


469. 


FIG.  470. 


FIG.  471. 


quires  the  cutter  to  be  used  as  an  end  mill,  a  threaded  hole  is 
substituted  for  the  plain  one  and  the  cutter  held  on  the  end  of  a 
suitable  screw  arbor.  These  cutters  are  regularly  made  with 
4°>  45 >  5°>  6o>  70  or  80  degree  angles,  either  right  or  left-handed. 
In  all  of  the  cutters  above  referred  to,  the  teeth  are  sharpened 
by  grinding  from  their  top  edges,  and  since  the  surfaces  milled 
are  either  planes  or  warped  planes,  the  contour  of  the  surface 
milled  is  not  changed  by  so  grinding  the  cutter.  In  form  mill- 


34-O  MODERN    MACHINE   SHOP   TOOLS. 

ing,  however,  the  teeth,  if  so  ground,  would  lose  their  outline 
and  would  therefore  not  produce  correct  work  after  being  sharp- 
ened. This  difficulty  is  overcome  by  the  use  of  the  formed  cut- 
ter, an  example  of  which  is  shown  in  Fig.  471.  This  cutter  is 
sharpened  by  grinding  from  the  front  face,  A,  of  each  tooth. 
The  cross-section  of  each  tooth  is  the  same  from  front  to  back 
faces.  The  back  face,  B,  being  somewhat  nearer  the  center  of 
the  cutter  than  face  A,  provides  the  necessary  tooth  clearance. 
The  sharpening  of  this  cutter  simply  reduces  slightly  its  diam- 
eter, which  has  no  effect  on  the  contour  of  the  machined  surface, 
the  cutter  being  adjusted  for  depth  after  each  grinding. 

The  original  application  of  this  method  of  forming  the  teeth 
was  on  gear  cutters,  but  it  has  since  been  adapted  to  nearly  all 


FIG.  472. 

classes  of  irregular  outline  cutters  used  for  form  milling.  Fig. 
472  shows  at  A  a  new  gear  cutter  and  at  B  a  similar  cutter,  which 
has  finished  complete,  at  one  cut  in  cast  iron,  gear  teeth  aggre- 
gating a  total  length  of  7,472  feet,  the  necessary  grinding  to  keep 
the  cutter  in  proper  working  condition  having  reduced  the  teeth 
to  the  shape  shown  in  the  figure.  The  last  tooth  cut  was,  how- 
ever, quite  as  accurate  in  form  as  the  first. 

In  Fig.  473  is  shown  a  group  of  formed  milling  cutters.  The 
names  of  these  cutters,  as  given  below,  refer  to  the  special  class 
of  work  each  is  designed  to  perform.  A  is  a  sprocket  wheel 
cutter ;  B,  cutter  for  fluting  reamers ;  C,  for  grooving  taps ;  D,  for 
cutting  twist  drills ;  E,  circular  cornering  cutter ;  F,  concave  cut- 
ter, and  G,  a  convex  cutter.  The  hob  cutter,  Fig.  474,  used  for 
cutting  the  teeth  of  worm  gears,  has  formed  teeth.  Angular  cut- 
ters with  formed  teeth,  Fig.  475,  are  now  quite  extensively  used. 


MILLING    MACHINE    CUTTERS. 


341 


They  are  the  only  cutters  regularly  made  with  formed  teeth  that 
are  used  on  work  not  classed  under  the  head  of  formed  work. 

The  method  by  which  the  relieved  teeth  are  produced  is  brief- 
ly outlined  in  the  following.     The  cutter  which  is  to  form  the 


FIG.  473. 

teeth  is  an  exact  negative  in  outline  to  the  outline  of  the  required 
tooth.  The  form  of  the  space  required  is  very  carefully  laid  out 
with  a  fine  scriber  on  a  piece  of  smoked  sheet  zinc.  The  zinc 


FIG.  474- 


FIG.  475. 


is  then  cut  away,  forming  a  template,  to  which  the  cutter  is  care- 
fully fitted;  the  final  fitting  of  the  cutter  to  the  template  being 
made  by  oil-stoning  after  it  is  tempered.  This  work  requires  the 
best  of  skill,  and  when  a  cutter  is  once  perfectly  formed,  other 


342  MODERN    MACHINE   SHOP   TOOLS. 

cutters  may  be  made  from  the  first  milling  cutter  it  produces. 
These  cutters  are  made  on  the  end  of  a  bar  of  steel  and  are  as 
thin  at  the  cutting  end  as  strength  will  permit  their  being  made. 

Take,  for  example,  the  gear  cutter  A,  Fig.  472.  It  is  first 
blanked  to  nearly  the  exact  dimensions,  the  spaces  which  separ- 
ate the  teeth  cut  and  the  blank  secured  on  a  rigid  arbor,  which 
is  driven  in  a  special  machine  at  a  slow  rate  of  rotation.  In 
front  of  the  blank  is  mounted  the  outlining  cutter  in  such  a  man- 
ner that  it  is  given  a  small  in-and-out  motion  once  per  revolu- 
tion for  every  tooth  to  be  cut.  When  the  cutter  begins  to  cut 
at  the  face  A,  it  is  farthest  from  the  center  of  the  blank,  and  as 
the  tooth  advances  to  the  face  B,  the  cutter  moves  toward  the 
center,  thus  cutting  the  tooth  deeper  at  B  than  at  A.  While  the 
blank  is  turning  through  the  space  to  the  next  tooth  the  cutter 


FIG.  476. 

backs  quickly  to  its  outer  position  and  repeats  its  motion  for  each 
tooth,  until  all  are  properly  formed. 

Relieved  tooth  cutters  are  made  from  solid  stock  as  large  as 
seven  inches  in  diameter  and  six  inches  in  length.  It  is  usual 
to  make  these  large  cutters  in  sections,  as  shown  in  Fig.  476. 
Such  combinations  of  cutters  are  termed  gang  mills,  and  may 
frequently  be  made  up  largely  of  standard  cutters.  In  the  one 
shown,  only  the  middle  section  is  a  formed  cutter,  the  balance 
being  regular  stock  cutters. 

What  is  known  as  the  fly  cutter  is  the  simplest  of  the  formed 
mills,  and  makes  a  cutter  well  adapted  to  small  jobs  of  special 
work,  where  the  expense  of  a  regular  form  cutter  would  not  be 
warranted.  The  fly  cutter  consists  of  a  single  tooth  mounted 
in  an  arbor.  In  making  the  cutting  tooth  the  stock  is  set  slightly 
back  from  the  center,  and  is  then  turned  in  a  lathe  to  the  desired 
outline,  tempered  and  reset  in  the  arbor,  this  time  with  a  liner 
behind  it,  which  throws  it  forward  until  the  front  face  comes 
radial,  and  gives  the  tooth  the  desired  clearance. 


MILLING    MACHINE    CUTTERS.  343 

As  already  indicated,  the  inserted  tooth  is  virtually  the  only 
practical  method  of  making  very  large  milling  cutters.  The  prin- 
cipal difference  in  cutters  of  this  class  lies  in  the  form  of  tooth 
and  the  method  of  securing  it  in  the  head.  Inserted  tooth  cut- 
ters necessarily  have  fewer  teeth  per  inch  of  circumference  than 
solid  cutters.  This,  however,  is  considered  by  many  as  an  ad- 
vantage. It  certainly  is  on  some  classes  of  work,  as  when  too 
many  are  used  the  cut  per  tooth  is  too  fine,  the  metal  being 
scraped  rather  than  cut  away,  which  produces  excessive  friction 
with  a  tendency  to  glaze  the  surface  and  rapidly  dull  the  cutter. 

In  Fig.  477  is  shown  a  form  of  axial  milling  cutter,  which  is 
used  for  heavy  slabbing  work.  It  is  made  in  any  required  size 
and  constitutes  a  very  efficient  tool  for  heavy  work.  The  teeth 
are  round  pieces  of  tempered  steel  driven  firmly  into  the  soft 


core,  and  then  ground  in  place.  It  is  found  that  cutters  of  this 
class  do  smoother  and  better  work  when  the  teeth  are  irregu- 
larly spaced.  A  radial  mill  constructed  along  these  same  lines 
is  shown  in  Fig.  478.  Here  the  teeth  are  held  in  position  by  set. 
screws,  and  may  be  adjusted  out  when  much  worn.  A  plain 
disk  may  be  substituted  for  the  armed  head,  the  set  screws  put 
in  the  back  and  more  cutters  used  if  desired.  The  cutting  edges 
of  the  teeth  should  project  beyond  the  circumference  as  well  as 
the  face  of  the  disk.  Cutters  of  this  character  are  frequently 
made  of  very  large  diameter. 

Fig.  479  illustrates  an  inserted  tooth  plain  mill,  in  which  the 
teeth  are  nicked.  The  teeth  are  arranged  spirally,  and  the 
method  of  securing  them  in  the  head  is  apparent.  The  makers 
of  this  cutter  also  make  plain  solid  milling  cutters  with  the  divided 
tooth. 

Fig.  480  shows  a  pair  of  mills,  quite  similar  in  construction,  in 


344 


MODERN    MACHINE   SHOP   TOOLS. 


which  the  tapered  pins  spread  the  stock  an  amount  sufficient  to 
grip  firmly  the  teeth.  In  the  cutter  shown  in  Fig.  481  the  teeth 
are  pinched  in  their  seats  by  drawing  down  with  the  screws  the 


FIG,  480. 


FIG.  481, 


FIG.  482. 


FIG.  483. 


tapered  bushings.  This  cutter  is  a  form  of  large  end  mill  to  be 
carried  on  a  special  arbor.  In  Fig.  482  is  shown  a  shell  end  mill- 
ing cutter.  End  mills  larger  than  i^  inches  diameter  are  made 
in  this  form  with  either  straight  or  spiral  teeth.  The  hole  is 


MILLING    MACHINE    CUTTERS.  345 

parallel,  the  drive  coming  on  a  key  which  engages  the  keyway  cut 
across  the  butt  of  the  mill. 

The  inserted  tooth  is  well  adapted  for  use  in  cutters  that  must 
be  kept  up  to  fixed  dimensions,  as  the  teeth  when  dull  can  be 
set  out  and  reground  to  the  exact  required  dimensions. 

When  in  radial  cutters  of  the  class  shown  in  Fig.  464  a  fixed 
thickness  must  be  maintained,  they  are  made  as  shown  in  Fig.  483 
and  known  as  interlocking  cutters.  After  each  grinding  it  is 
necessary  to  put  thin  washers  between  the  sections  to  make  up  for 
the  reduction  in  thickness,  due  to  the  grinding.  With  large 
built-up  cutters,  interlocking  sections  are  generally  used  where 
fixed  widths  must  be  maintained. 

The  diameter  of  a  milling  cutter  should  be  as  small  as  the 
work  will  permit.  The  small  cutter  requires  less  power  to  drive 
it,  cuts  smoother,  keeps  sharp  longer,  makes  its  cut  on  a  shorter 
length  of  feed  than  a  large  cutter,  and  is  lower  in  first  cost. 
Plain  or  axial  cutters  can  usually  be  of  small  diameter  as  the  cut 
is  seldom  deep,  vand  the  surface  machined  requires  length  rather 
than  diameter  of  cutter.  This  is,  however,  reversed  in  the  face 
or  radial  mill,  where  the  diameter  of  cutter  depends  entirely 
on  the  width  of  the  surface  to  be  milled. 

Milling  cutters  are  usually  made  with  the  front  faces  of  the 
teeth  radial,  thus  giving  no  angle  of  rake.  The  angle  of  clear- 
ance should  be  about  3  degrees ;  the  width  of  the  top  of  the  tooth 
being,  before  the  first  grinding,  from  .02  to  .04  of  an  inch  wide. 

Too  much  stress  cannot  be  laid  on  the  importance  of  keeping 
milling  cutters  sharp,  and  especially  the  formed  cutters.  When 
a  cutter  starts  to  dull  it  begins  to  crush  and  remove  by  abrasion 
rather  than  cut  the  stock.  This  produces  excessive  friction  be- 
tween the  teeth  and  work,  and  unless  the  cutter  is  ground 
promptly,  its  edges  will  be  entirely  lost.  In  the  case  of  a  formed 
cutter,  when  dull,  a  few  revolutions  will  often  so  badly  snub 
the  teeth  that  a  fourth  or  even  more  of  each  tooth  will  be  ground 
away  before  their  perfect  section  is  reached.  This  is  a  tedious 
process,  and  unless  great  care  is  exercised  is  very  apt  to  result 
in  destroying  the  temper  on  one  or  more  of  the  teeth. 

The  grinding  of  formed  cutters  requires  an  emery  wheel  of 
thin,  dished  section  with  a  straight  face  at  the  edge.  The  tendency 
is  to  grind  too  much  from  the  outer  part  of  the  tooth  face, 
thus  making  a  negative  rake  angle  and  poor  cutting  teeth.  For 
grinding  the  ordinary  form  of  tooth,  a  thin  wheel  of  quite  large 


346  MODERN    MACHINE   SHOP   TOOLS. 

diameter  should  be  used.  If  the  diameter  is  small  the  top  of  the 
tooth  will  be  ground  concave  to  such  an  extent  that  the  cutting 
edge  will  be  materially  weakened.  By  so  mounting  the  wheel 
that  its  axis  is  not  parallel  with  that  of  the  cutter  it  will  grind 
the  top  of  the  tooth  flat.  This  is  not  ordinarily  done,  however. 
The  emery  wheel  used  for  this  purpose  should  be  a  free  cutting 
one,  and  not  too  fine,  as  a  fine  wheel  glazes  and  burns  the  delicate 
edge  of  the  tooth.  Its  grinding  face  should  be  thin,  and  the 
emery  about  No.  80. 

Milling  cutters  are  driven  from  the  machine  spindle  in  three 
ways.  Large  cutters  are  frequently  threaded  directly  to  the  nose 
of  the  spindle.  This  constitutes  a  most  rigid  and  very  satis- 
factory drive.  They  may  also  be  carried  on  stub  arbors,  which 


FIG.  484. 

are  either  a  part  of  or  separate  from  the  cutter,  and  lastly,  upon 
through  arbors,  which  may  be  supported  on  the  outer  end. 

The  small  cutters  of  the  end  mill  class  are  usually  provided 
with  a  taper  shank  and  a  tang  for  driving,  as  shown,  for  example, 
in  Fig.  468.  The  Brown  &  Sharpe  taper  of  ^  inch  per  foot  is 
the  taper  usually  given  the  shanks.  These  shanks  fit  either  di- 
rectly in  the  spindle  bearing  of  the  machine  or  in  the  collets  which 
serve  as  reducers. 

In  Fig.  484  are  shown  two  examples  of  milling  machine  col- 
lets. The  one  drives  from  a  tang,  the  other  from  a  flatted  collar, 
which  engages  in  a  slot  cut  across  the  nose  of  the  spindle.  These 
collets  are  quite  similar  to  drill  sleeves. 

Examples  of  stub  arbors  are  shown  in  Fig.  485.  The  shell 
end  mill  arbor  shown  at  A  is  used  to  carry  cutters  of  the  class 
shown  in  Fig.  482  with  parallel  holes.  The  arbor  shown  at  B 
has  a  tapered  nose  and  drives  the  cutter  by  the  key  shown.  The 
cutter  is  driven  tightly  on  the  nose  of  the  arbor  and  the  flat  head 


MILLING    MACHINE    CUTTERS. 


347 


screw  in  the  end  prevents  it  from  working  loose.  The  nut  shown 
runs  over  a  fine  pitch  thread  and  is  used  for  forcing  the  cutter  off. 
Cutters  of  the  class  shown  in  Fig.  481  are  usually  carried  on  an 
arbor  of  this  character.  In  the  case  of  milling  cutters  with 
threaded  holes,  a  screw  arbor  must  be  used.  If  the  cutter  is  of 
small  diameter  and  the  work  it  performs  light,  a  plain  threaded 
nose  which  allows  the  cutter  to  screw  up  squarely  against  a 


FIG.  485. 

shoulder  is  satisfactory.  If,  however,  the  cutter  is  large  and  its 
work  heavy  it  will  tighten  so  hard  that  difficulty  is  experienced  in 
starting  it  loose.  In  cases  of  this  kind  an  arbor  similar  to  the 
one  shown  in  Fig.  486  is  well  suited.  The  cutter  screws  onto 
the  nose  of  the  arbor  at  A.  B  is  a  clutch  collar  which  slides  on 
the  arbor  and  over  a  feather  key  D,  which  prevents  it  from  rotat- 
ing. E  E  is  a  nut  which  threads  over  the  collar  of  the  arbor. 


FIG.  486. 

In  applying  the  cutter  the  nut  E  E  is  screwed  close  up  to  the 
shoulder  and  the  clutch  collar  slid  back  as  far  as  possible.  The 
cutter  is  screwed  on  until  its  face  touches  the  keys  C  C,  which  are 
a  part  of  the  collar  B.  The  key  seats  in  the  back  face  of  the 
cutter  are  placed  opposite  the  keys  C  C,  and  the  clutch  collar 
moved  forward  engaging  the  keys.  The  nut  E  E  is  backed  up 
against  the  clutch,  holding  all  parts  firmly.  In  removing  the 
cutter  it  is  simply  necessary  to  slack  the  nut  and  draw  back  the 


348 


MODERN    MACHINE   SHOP   TOOLS. 


clutch,  thus  leaving  the  cutter  free  to  turn  off.  Threaded  cut- 
ters, when  left-handed  should  have  left-hand  threaded  holes  and 
when  right-handed  should  have  right-hand  threads  in  the  hole, 


FIG.  487. 

as  otherwise  the  pressure  of  the  cut  will  tend  to  loosen  the  cutter 
from  its  arbor. 

In  Fig.  487  is  shown  a  spring  chuck  collet  used  on  the  mill- 


FIG.  488. 


ing  machine  -for  holding  small  cutters  having  parallel  shanks ;  an 
example  of  such  a  cutter  being  shown  in  Fig.  488. 

Milling  machine  cutter  arbors,  an  example  of  which  is  shown 
in  Fig.  489,  are  fitted  to  the  spindle  bearings  and  driven  in  the 


FIG.  489 

same  manner  as  the  collets.  The  extended  portion  of  the  arbor  is 
ground  cylindrically  true  and  provided  with  a  nut  at  or  near  its 
outer  end  for  clamping  the  cutter  between  the  washers.  The 
arbor  washers  are  of  assorted  lengths  in  order  to  accommodate 


MILLING    MACHINE    CUTTERS.  349 

cutters  of  different  thickness.  „  When  the  overhanging  arm  sup- 
ports the  bar  at  the  end,  a  suitable  bearing  is  provided  on  the 
end  of  the  arbor.  For  supporting  the  bar  midway  in  its  length, 
a  collar  somewhat  larger  in  diameter  than  the  others  fits  a  suit- 
able bushing  in  the  overhanging  arm.  Arbor  nuts  should  be 
right  or  left-handed,  depending  upon  the  direction  of  rotation,  as 
a  slipping  cutter  should  tend  to  tighten  rather  than  loosen  the 
nut.  Cutters  of  small  diameter  can  usually  be  driven  by  the 
friction  between  washers  and  cutters  alone.  Larger  sizes,  how- 
ever, should  be  keyed  to  the  arbor  and  for  this  purpose  a  spline  is 
cut  the  full  length  of  the  arbor. 

In  putting  collets  and  arbors  in  their  bearings  in  the  spindle, 
both  surfaces  should  be  wiped  clean  and  dry  and  driven  snugly 
together.  A  soft  hammer  or  block  of  hard  wood  should  always 
be  used  to  drive  with. 


CHAPTER  XXV. 

MILLING   MACHINE  WORK. 

Dividing  a  circle  into  equal  parts  by  means  of  the  plain  or 
universal  spiral  head  on  the  milling  machine  is  known  as  "index- 
ing." When  the  index  plate  is  secured  to  the  spindle  as  at  C, 
Fig.  448,  and  the  divisions  obtained  by  rotating  the  plate  and 
spindle  together,  it  is  known  as  direct  indexing.  When  the 
spindle  is  rotated  by  means  of  suitable  geared  connections  and  the 
index  plate  remains  normally  stationary  the  term  indirect  index- 
ing is  usually  applied.  The  indirect  method  can  be  classified 
under  three  heads,  simple,  compound  and  differential. 

Since,  as  shown  in  Fig.  448,  forty  turns  of  the  crank  J  and 
worm  A  are  required  to  make  one  turn  of  the  spindle  the  follow- 
ing rule  for  simple  indirect  indexing  may  be  given.  Take  40  as 
the  numerator  and  the  required  number  of  divisions  as  the 
denominator,  and  reduce.  Thus,  it  is  required  to  cut  32  teeth 
in  a  gear.  40-32,  or  I  8-32  of  one  revolution  of  the  crank  will 
make  one  division  on  the  blank. 

The  sector  should  be  set  to  include  8  spaces  (9  holes)  on  the 
32  circle,  or  4  spaces  on  the  16  circle  could  be  used.  If  108  teeth 
were  required,  then  40-108  =  20-54=  10-27,  or  10  spaces  on  the 
27  circle  would  give  the  required  division.  This  ratio  is  not 
affected  by  multiplying  or  dividing  both  numerator  and  de- 
nominator by  the  same  number.  Therefore  after  reducing  as 
low  as  possible,  if  that  denominator  does  not  correspond  to 
the  number  of  holes  in  any  circle  available,  we  can  multiply  or 
divide  it  by  any  number  that  would  give  us  the  proper  number, 
also  treating  the  numerator  in  the  same  manner.  For  example, 
25  divisions  require  40-25  =  I  3-5  turns.  We  can  use  any  circle 
divisible  by  5,  as  20,  or  4  times  the  denominator.  Multiplying 
the  numerator  by  4  also,  gives  12  holes  in  the  20  circle. 

It  frequently  becomes  necessary  to  divide  a  circle  into  a  num- 
ber of  parts  which  can  not  be  obtained  in  the  regular  manner 
because  a  circle  of  the  required  number  of  holes  is  not  on  the 
index  plate.  If  a  circle  for  making  one-half  the  required  di- 
visions is  on  the  plate,  every  other  tooth  can  be  cut ;  the  work 
can  then  be  rotated  through  one-half  of  one  space  and  the  bal- 


MILLING    MACHINE    WORK.  351 

ance  of  the  teeth  cut.  Thus  if  96  teeth  are  required  and  no 
circle  available,  set  for  cutting  48  teeth,  which  gives  10  spaces 
in  the  12  circle  or  15  spaces  in  the  18  circle.  After  cutting  once 
around,  move  the  pin  through  7^  spaces,  and  being  careful  that 
it  is  not  moved,  cut  partly  through  on  the  tooth;  stop  the  ma- 
chine without  throwing  out  the  feed  and  carefully  adjust  the 
driver  to  make  up  for  the  ^2  space,  which  brings  the  pin  into 
another  hole,  and  proceed  with  the  cutting  as  for  the  first  half. 
With  care  in  the  adjustment,  the  error  in  making  the  ^2  setting 
will  be  slight. 

A  method  of  compound  indexing  can  be  used  to  excellent  ad- 
vantage for  obtaining  with  the  regular  plates  many  divisions 
that  may  not  be  had  in  the  regular  manner.  The  application  of 
this  method  requires  plates  with  the  holes  drilled  through,  and 
the  back  pin  R,  Fig.  448,  radially  adjustable.  The  method  con- 
sists in  indexing  forward  on  the  front  side  of  the  plate  in  the  regu- 
lar manner  and  adding  to  or  subtracting  from  this  movement  an- 
other movement  indexed  from  the  back  side  of  the  plate.  From 
tables  calculated  by  W.  Gribbons  and  given  complete  in  "Con- 
struction and  Use  of  Milling  Machines,"  a  treatise  published 
by  the  Brown  &  Sharpe  Mfg.  Co.  To  divide  into  91  parts,  index 
forward,  on  the  front  of  the  plate,  six  spaces  on  the  39  circle; 
then  index  forward  on  the  back  of  the  plate,  14  spaces  on  the 

6        14        2        14      98  +  182       280       40 

49  circle.     This  gives 1 — h  - 

39       49       13       49          637  637       91 

or  the  equivalent  of  40  holes  in  a  91  circle.  If  99  spaces  are 
required,  index  forward  15  spaces  on  the  27  circle  and  backward 

T5        5         5        5 
5    spaces   on   the   33    circle.     This   gives   - 

27       33        9        33 

165  —45  120  40 

=  =  — ,  or  the  equivalent   of    40    holes    in   a   99 

297  297       99 

circle. 

For  the  two  cases  above  given  the  method  is  exact.  For  a 
large  number  of  the  divisions  practically  possible  the  method  is 
approximate.  For  example,  to  divide  into  212  parts.  34~47 
turns  forward  plus  6-49  of  a  turn  forward  gives  211.9995  teeth, 
a  division  sufficiently  accurate  for  all  practical  purposes.  In 
this  case  the  teeth  are  not  successively  cut,  17  turns  of  the  work 
being  required  in  which  to  catch  all  of  the  divisions. 


352 


MODERN    MACHINE   SHOP   TOOLS. 


The  above  method  is  unique  and  will  frequently  be  found  of 
great  value.  Care  must  be  exercised  in  making  the  moves,  as 
the  chances  for  mistakes  are  great,  especially  so  as  the  back- 
plate  moves  necessitates  counting  the  holes  each  time,  a  sector 
not  being  provided. 

The  new  method  of  differential  indexing,  as  applied  by  the 
Brown  &  Sharpe  Mfg.  Co.  to  all  their  universal  spiral  heads,  is 
an  exact  method  which  not  only  overcomes  the  chances  of  error 
in  the  compound  method,  but  is  much  more  convenient. 

The  spiral  head  is  shown  in  Fig.  490,  also  in  sectional  views  in 
Fig.  448.  Referring  to  these  figures,  an  extended  shaft  from 
the  spindle  carries  a  gear  E,  which  through  the  idler  D  and  the 


PIG.  490. 

gear  C  communicates  the  motion  of  the  spindle  to  the  gear  train 
Fig.  449,  connected  with  the  index  plate  I.  When  pin  P,  Fig. 
448,  engages  a  hole  in  the  plate  the  whole  becomes  a  locked 
mechanism.  Withdrawing  P  unlocks  the  mechanism  and  the 
rotation  of  the  crank  J,  worm  A  and  spindle  causes  index  plate  I 
to  rotate  either  right  or  left  handed,  depending  on  whether  one 
idler,  D,  or  two  are  used,  and  the  amount  of  motion  relative  to 
the  crank  is  governed  by  the  gears  used. 

If  gears  E  and  C  are  of  the  same  diameter,  one  turn  of  the 
spindle  will  make  one  turn  of  the  index  plate.  This  will  require 
40  turns  of  the  crank  J  and  as  the  rotation,  due  to  using  one 
idler,  is  in  the  same  direction,  the  pin  P  has  passed  a  given  point 
on  the  index,  but  39  times,  thus  giving  39  as  the  spacing  number. 


'TV 

' 

MILLING    MACHINE    WORK.  353 

Had  two  idlers  been  used  the  rotation  would  have  been  in  oppo- 
site directions  and  41  would  have  been  the  spacing  number  inas- 
much as  the  plate  has  gained  a  crank  rotation. 

The  manufacturers  furnish  a  complete  table  of  change  gears 
for  dividing  all  numbers  up  to  360.  Take  for  example  the  division 
317 — referring  to  the  table — gear  64  should  be  used  on  the  worm 
C,  and  gear  24  on  the  spindle  E,  with  one  idler.  The  ratio  of 
worm  to  spindle  rotation  is  f  j-  =  ^  and  as  the  plate  and  crank  ro- 
tate in  the  same  direction,  the  spindle  loses  y%  of  one  revolution 
for  every  40  revolutions  of  the  crank,  or  3  full  revolutions  in  320 
turns  of  the  crank  giving  317  as  the  number  of  divisions.  Set 
the  sector  to  give  l/%  turn  of  the  crank,  or  3  spaces  on  the  24 
circle. 

When  the  required  ratio  would  give  gears  too  large  or  too 
small  in  diameters  they  are  compounded,  thus  keeping  diameters 
within  reasonable  limits.  Spirals  cannot  be  cut  when  the  head  is 
geared  for  differential  indexing. 

For  correct  indexing  there  should  be  no  slack  or  back  lash 
in  any  of  the  parts.  It  is  advisable,  however,  not  to  carry  the 
crank  and  its  pin  past  the  hole,  but  to  bring  it  up  to  the  hole 
without  the  necessity  of  carrying  it  back,  which  would  serve  to 
let  any  slack  affect  the  accuracy  of  the  division.  It  is  advisable, 
in  order  to  prevent  confusion,  for  the  operator  always  to  rotate 
the  crank  in  the  same  direction,  unless  there  is  some  special  rea- 
son for  doing  otherwise. 

The  radial  arms  of  the  sector  are  held  in  position  with  refer- 
ence to  each  other,  by  friction.  In  rotating  them  over  the  face 
of  the  plate,  always  take  hold  of  the  arm  that  strikes  the  pin,  as 
there  will  then  be  no  danger  of  changing  their  relative  position 
through  striking  the  pin  with  considerable  force. 

In  Fig.  491  is  shown  an  end  view  of  the  dividing  head,  de- 
scribed in  Fig.  448,  secured  on  the  end  of  the  work  table.  The 
spindle  S  carries  a  spiral  gear  at  its  farther  end,  meshing  with 
the  upper  spiral  gear  shown  in  Fig.  449.  The  gear  marked 
''screw"  is  keyed  to  the  feed  screw  and  through  the  compound 
idlers  transmits  its  motion  to  the  gear  on  worm  and  through  the 
spirals  and  spur  gear  connection  to  the  worm  and  worm  gear. 
\Vhen  the  spindle  is  so  geared  the  post  R  is  disengaged  from  the 
plate  and  the  worm  shaft  is  driven  from  the  dividing  plate  through 
the  pin  P  and  the  crank  J.  It  is  obvious  that  when  the  feed 
screw  is  at  rest,  the  plate  I  is  held  without  the  pin  R  and  the  re- 


354 


MODERN    MACHINE    SHOP    TOOLS. 


quired  divisions  obtained  by  carrying  the  crank  over  the  plate  in 
the  usual  manner. 

With  all  universal  machines  a  table  of  change  gears  is  pro- 
vided for  determining  the  proper  gears  to  use  for  producing  a 
large  number  of  spirals  of  different  pitch.  Any  desired  pitch  of 
spiral  can  be  obtained  by  making  special  gears,  and  a  good  many 
pitches  not  given  in  the  table  may  be  produced  by  other  combi- 
nations of  the  regular  gears  than  those  given.  The  proper  gear 


FIG.  491. 


for  a  required  spiral  pitch  may  be  readily  determined  from  the 
following  considerations. 

The  table  lead  or  feed  screws  usually  have  four  threads  per 
inch.  Assuming  that  number,  if  the  gear  of  the  screw  had  the 
same  number  of  teeth  as  the  one  on  the  spindle  S  and  was  geared 
directly  with  it  (that  is,  simple,  not  compound  geared),  then  40 
turns  of  the  screw  would  make  40  turns  of  the  worm  and  one 
of  the  spindle;  and  as  four  turns  of  the  screw  are  required  per 
inch  of  the  table  motion,  the  pitch  of  the  spiral  would  be  10 
inches.  If  a  spiral  pitch  of  6  inches  was  required,  6x4  =  24, 


MILLING    MACHINE    WORK.  355 

the  number  of  revolutions  the  screw  must  make  while  the  work 
rotates  through  one  revolution.     Then  the  ratio 
24      teeth  in  driven  gear 

40      teeth  in  driving  gear 

Put  gear  with  40  teeth  on  the  screw  and  gear  with  24  teeth  on  the 
spindle  S.  It  is  best  when  possible  to  use  the  simple  gearing.  If, 
however,  the  ratio  is  such  that  one  of  the  gears  would  be  extremely 
large  or  small,  then  the  gearing  should  be  compounded.  For 
example,  required  pitch  of  spiral  32^2  inches ;  32^2  x  4  ~  130, 
or  the  revolutions  of  the  screw  per  revolution  of  the  work 
130  No.  teeth  in  driven  gear 

40       No.  teeth  in  driving  gear 

As  130  would  be  a  rather  large  gear  and  probably  not  furnished 
with  the  machine  we  could  reduce  the  ratio  to  |^,  but  this  would 
also  give  numbers  of  teeth  not  usually  furnished.  It  would  then 
be  necessary  to  compound.  Resolve  the  ratio  *££-  into  fac- 
tors ^-X-1/.  As  these  numbers  are  too  low  we  can  multiply  both 
numerator  and  denominator  by  the  same  number,  and  we  would 
have,  for  example,  -^  X  £  =  f$  and  -^  x  J  =  -||  and  as 
M  x  H  =  tne  ratio  ±f£  we  may  use  gears  40  and  52  as  the 
driven  gears.  Either  20  or  32  can  be  placed  on  the  screw  and 
the  other  will  be  the  inside  gear  on  the  stud.  Either  the  40  or 
52  can  be  put  on  the  worm  shaft  S  and  the  other  -will  be  the 
outside  gear  on  the  stud.  If  any  of  the  gears  called  for  were 
not  found  in  the  regular  set,  the  numbers  could  be  changed  by 
treating  both  numerator  and  denominator  without  changing  the 
ratio.  Thus  in  the  last  problem,  if  the  last  set  did  not  contain 
a  gear  of  20  teeth,  we  could  divide  both  numerator  and  denomi- 
nator by  a  common  factor  and  multiply  the  results  by  a  number 
that  would  give  numbers  corresponding  to  available  gears.  Thus 
in  the  ratio  j-J-  divide  both  by  5  =  f  and  multiply  both  by  6. 
This  would  give  |f ,  which  alters  the  numbers  but  does  not  change 
the  ratio.  In  this  manner  it  is  usually  possible  to  so  manipulate 
the  ratios  that  the  exact  or  a  very  close  approximation  to  the  re- 
quired pitch  can  be  obtained  with  the  regular  gears. 

The  arrangement  shown  in  Fig.  449  gives  the  proper  rotation 
for  cutting  a  right-hand  spiral.  If  a  left-hand  spiral  is  required  a 
reverse  gear  must  be  put  into  the  series.  This  gear  is  carried  on 
a  suitable  arm,  and  the  gear  marked  40  drives  72  through  this 


356  MODERN    MACHINE    SHOP    TOOLS. 

gear,  thus  changing  the  direction  of  rotation  of  the  worm  shaft 
and  spindle. 

In  the  cutting  of  all  spirals  the  work  table  must  be  set  at  an 
angle  with  the  cutter's  axis,  an  amount  equal  to  the  spiral  angle 
of  the  work.  For  equal  pitch  of  spiral  this  angle  varies  with  the 
diameter  of  the  work;  the  larger  the  diameter  the  greater  the 
angle. 

In  the  cutting  of  any  spiral  the  pitch  of  the  spiral,  the  spiral 
angle,  the  number  of  teeth  and  the  form  of  the  cutter  must  be 
known.  Having  this  data,  the  work  is  placed  between  centers 
and  the  cutter  brought  over  its  center.  The  proper  change  gears 
for  giving  the  required  pitch  are  adjusted  and  the  table  swung 
toward  the  column  the  amount  of  the  spiral  angle.  The  rota- 
tion of  the  spindle  must  be  left-handed  for  left-handed  spirals, 
and  right-handed  for  right-handed  spirals,  this  change  in  di- 
rection of  rotating  being  obtained  by  putting  in  or  taking  out 
an  idle  gear  in  the  change  gear  mechanism. 

The  proper  rotative  speeds  and  feeds  are  very  important 
as  they  are  the  principal  factors  upon  which  the  output  of  the 
machine  depends.  As  the  toughness  and  hardness  of  the  differ- 
ent grades  of  the  several  metals  varies  so  much,  it  is  impossible 
to  lay  down  any  fixed  rules  to  be  followed.  With  cutters  other 
than  the  most  delicate  the  very  fine  feeds  are  to  be  avoided,  as 
the  cutting  edges  stand  up  better  under  a  moderately  heavy  cut 
than  when  scraping  the  metal  away. 

Milling'  cutters  must  be  kept  sharp.  As  soon  as  a  cutter 
loses  its  keen  cutting  edges  it  dulls  very  quickly  and  does  not 
produce  smooth  or  accurate  surfaces  as  it  springs  away  from  its 
work.  A  cutter  must  not  be  run  backward  when  against  its  cut, 
as  the  teeth  are  not  strong  against  a  backing  pressure  and  are 
apt  to  be  broken  off. 

For  the  standard  carbon  steel  milling  cutters,  a  surface  speed 
of  30  to  40  feet  per  minute  can  be  maintained  on  soft  machinery 
steel,  thoroughly  annealed  tool  steel  and  wrought  iron.  In  such 
cases,  however,  the  cutters  should  be  sharp  and  lubricated  with 
screw  cutting  oil  or  some  good  compound.  On  cast  iron  cutting 
speeds  of  from  40  to  60  feet  per  minute  can  be  maintained,  de- 
pending on  the  hardness  of  the  iron.  On  brass  a  speed  of  from 
80  to  100  feet  per  minute  is  suitable.  These  speeds  may,  with 
cutters  made  of  special  air  hardening  steels,  be  materially  in- 
creased. 


MILLING    MACHINE    WORK. 


357 


.The  depth  of  cut  and  rate  of  feed  employed  are  dependent 
upon  the  hardness  of  the  metal,  its  strength  to  resist  the  cut, 
rigidity  with  which  it  is  held,  and  character  of  finished  surface 
required. 

In  general  finishing  cuts  with  plain  axial  mills  are  taken  at 
quick  speeds  and  fine  feeds.  With  radial  mills'  finishing  cuts 
may  be  taken  at  coarse  feeds,  as  the  character  of  the  cut  due  to 
the  long  cutting  edge,  does  not  show  a  waved  or  uneven  sur- 
face. 

In  the  case  of  expensive  gangs  of  cutters,  and  more  especially 
on  those  where  fixed  dimensions  necessitate  great  care  in  grind- 
ing, it  is  advisable  to  hold  the  cutting  speed  down  somewhat. 

The  following  table  will  be  found  convenient  for  determin- 
ing the  proper  number  of  revolutions  for  cutters  of  different 
diameter  to  give  cutting  speeds  up  to  60  feet  per  minute. 

TABLE  OF  CUTTING  SPEEDS. 


Feet  per        r' 
Minute.        ^ 

10' 

15' 

20' 

25' 

30'    |    35' 

4o'        45' 

50'      |      60' 

Diana. 

REVOLUTIONS  PER  MINUTE. 

X  38.2 

76.4 

114.6 

152.9 

191.1 

229.3 

267.5 

305.7 

344.0 

382.2 

458.7 

X\  30.6 

61.2 

91.8 

122.5 

I53.I 

183-7 

214.3 

244.9 

275.5 

306.1 

367.5 

X\  25-4 

50.8 

76.3 

101.7 

127.1 

152-5 

178.0 

203.4 

228.8 

254.2 

305.1 

H   21.8 

43-6 

65.5 

87.3 

109.1 

130.9 

152.7 

174.5 

196.3 

218.9 

261.9 

i      19.1 

38.2 

57-3 

76.4 

95-5 

114.6 

133.8 

152.9 

172.0 

I9I.I 

229.2 

I#  17.0 

34-0 

51.0 

68.0 

85.0 

IO2.O 

119.0 

136.0 

153.° 

I7O.O 

2O4.O 

iX  15-3 

30.6 

45-8 

61.2 

76.3 

91.8 

106.9 

122.5 

137.4 

I53-I 

183.6 

i#  13-9 

27.8 

41.7 

55-6 

69-5 

83.3 

97-2 

in.  i 

125.0 

138.9 

166.8 

i#  12.7 

25-4 

38.2 

50.8 

63-7 

76.3 

89.2 

101.7 

114.6 

I27.I 

152.4 

'i#    11.8 

23-5 

35-o 

47-o 

58.8 

70.5 

82.2 

93-9 

105.7 

II7.4 

I4I.O 

I#  10.9 

21.8 

32.7 

43-6 

54-5 

65.5 

76.4 

87.3 

98.2 

IO9.I 

130.8 

1%     10.2 

20.4 

30.6 

40-7 

50.9 

61.1 

71-3 

81.5 

91.9 

IOI.9 

122.  1 

2 

9.6 

19.1 

28.7 

38.2 

47-8 

57-3 

66.9 

76.4 

86.0 

95-5 

II4.6 

2X1    8-5 

17.0 

25-4 

34.o 

42.4 

51.0 

59-4 

68.0 

76.2 

85-0 

IO2.O 

a#:    7-6 

15-3 

22.9 

30.6 

38.2 

45-8 

53-5 

61.2 

68.8 

76.3 

91.8 

2^ 

6.9 

13-9 

20.8 

27.8 

34-7 

41.7 

48.6 

55-6 

62.5 

69-5 

83.4 

3 

6.4 

12.7 

19.1 

25-5 

31.8 

38-2 

44-6 

51-0 

57-3 

63-7 

76.5 

$y* 

5-5 

10.9 

16.4 

21.8 

27.3 

32.7 

38.2 

43-6 

49.1 

54-5 

65.4 

4 

4-8 

9.6 

14.3 

19.1 

23-9 

28.7 

33-4 

38.2 

43-0 

47-8 

57-3 

*% 

4.2 

8.5 

12.7 

16.9 

21.2 

25-4 

29.6 

34-0 

38-1 

42.4 

50.7 

3-8 

7-6 

n-5 

15-3 

I9.I 

22.9 

26.7 

30.6 

34-4 

38.2 

45-9 

5% 

3-5 

6.9 

10.4 

13-9 

17.4 

20.8 

24-3 

27.8 

3!-3 

34.7 

41.7 

6 

3-2 

6.4 

9.6 

12.7 

15.9 

19.1 

22.3 

25-5 

28.7 

3i.8 

38.1 

7 

2.7 

5-5 

8.1 

10.9 

13-6 

16.4 

19.1 

21.8 

24.6 

27-3 

32.7 

8- 

2.4 

4.8 

7-2 

9-6 

II.9 

14.3 

16.7 

19.1 

21.  1 

23-9 

28.8 

Q 

2.1 

4.2 

6.4 

8.5 

10.6 

12.7 

14-9 

17.0 

I9.I 

21.2 

25-5 

10         1.9 

3-8 

5-7 

7-6 

9.6 

11.5 

13-4 

15.3 

17.2 

I9.I 

22.8 

The  smaller  milling  cutters  which  are  carried  on  an  arbor 
are  usually  driven  by  the  friction  between  their  faces  and  the 
arbor  collars.  They  should  therefore  be  rotated  in  the  direction 


358 


MODERN    MACHINE    SHOP    TOOLS. 


which  tends  to  tighten  the  arbor  -nut.  With  the  large  cutters 
which  are  keyed  to  the  arbor  the  direction  of  rotation  may  be 
either  way.  For  a  given  rotation  of  the  cutter  the  direction  of 
the  feed  should  be  such  as  to  force  the  work  against  the  cutter 
as  shown  at  A,  Fig.  492.  When  the  rotation  and  feed  are  as 
above  indicated,  all  slack  or  back  lash  between  the  nut  and  feed 
screw  is  taken  up  and  the  work  is  forced  steadily  to  its  cut.  If 
the  feed  is  as  shown  at  B,  the  cutter  tends  to  drag  the  work  under 
it  and  as  a  result  any  slack  whatever  allows  the  work  to  move 
forward  with  an  unsteady,  irregular  motion  as  the  feed  screw 
rotates.  When  the  feed  is  as  shown  at  A,  the  cutter  teeth  work 
from  the  bottom  up,  lifting  the  hard  scale  of  castings  and  forg- 
ings  rather  than  cutting  down  upon  it,  as  is  the  case  when  the 


FIG.  492. 

feed  is  as  shown  at  B.  The  keen  edge  of  the  cutter  lasts  much 
longer  with  the  feed  in  the  direction  indicated  at  A.  The  under 
feed  indicated  at  B  has  been  advocated  by  some,  but  is  generally 
considered  as  incorrect,  as  the  wear  on  the  cutter  and  the  danger 
of  accident  from  the  work  drawing  under  is  much  greater.  With 
milling  machines  using  the  rack  feed  where  the  work  table  is  held 
only  when  the  feed  is  in,  the  most  careful  workman  will  some- 
times get  into  trouble  if  the  under  feed  B  is  used. 

When  the  cutter  is  operating  on  the  end  of  the  work  as 
shown  at  D,  the  feed  should  be  up,  as  indicated  by  the  arrow; 
if  the  work  was  on  the  other  side  of  the  cutter,  the  feed  should 
be  down.  In  this  class  of  milling  it  is  best  to  feed  up,  as  that 
brings  the  pressure  of  the  cut  down  upon  the  table  and  tends  to 
close  the  joints  of  the  table,  saddle  and  knee,  making  the  cut 
smooth  and  steady.  When  the  table  is  to  be  fed  vertically  for 


MILLING    MACHINE    WORK.  359 

work  as  shown  at  D,  the  table  stops,  provided  with  all  milling 
machines,  should  be  used  and  thus  prevent  any  possibility  of  the 
work  moving  in  or  away  from  the  cutter  when  correctly  set. 
When  it  is  necessary  to  use  both  sides  of  the  cutter  at  the  same 
time,  as  in  Fig.  493,  the  direction  of  the  feed  should  be  deter- 
mined from  a  consideration  of  the  amount  of  stock  to  be  re- 
moved from  the  sides.  If  the  rotation  of  the  cutter  is  as  indicated 
and  the  most  stock  is  to  be  removed  from  the  surface  A,  then  the 
feed  should  be  in  the  direction  shown  by  the  arrow.  The  cut  on 
the  upper  surface  then  tends  to  retard  the  feed  and  the  cut 
on  the  lower  surface  to  draw  the  feed ;  and  since  the  cut  on 
the  upper  surface  is  heavier  than  that  on  the  lower,  the  re- 
tarding pressure  is  greater  than  the  drawing,  and  a  smooth, 
steady  cut  results,  with  a  minimum  danger  of  injury  to  the 


FIG.  493. 

work  and  cutter.  If  the  cut  was  heaviest  at  the  surface  B, 
the  cutter  should  be  started  from  the  opposite  end  and  the  direc- 
tion of  the  feed  reversed. 

Plain  surfaces  may  usually  be  milled  either  by  the  plain 
axial  milling  cutter  or  a  radial  or  end  mill.  The  axial  cutter 
leaves  a  smoother  surface  and  is  more  easily  kept  in  order  than 
the  radial.  The  tendency  to  spring  and  distort  the  work  is, 
however,  greater  with  the  axial  cutter,  as  the  pressure  of  the  cut 
is  very  largely  at  right  angles  to  the  work  surface,  while  with 
the  end  mill  the  pressure  is  almost  wholly  in  the  direction  of 'the 
feed.  The  character  of  the  work  usually  determines  which  class 
of  cutter  to  use.  At  i  and  2,  Fig.  494,  are  shown  two  ways  of 
milling  a  common  hexagon  nut.  The  straddle  mills  of  No.  2 
are  radial  cutters  and,  as  arranged,  finish  two  surfaces  each 
time  over  the  work.  An  end  mill  might  be  used,  in  which  casa 
but  one  surface  would  be  finished  at  a  time.  In  any  case  the 
diameter  of  the  mill  should  be  as  small  as  strength  and  con- 


360 


MODERN    MACHINE    SHOP   TOOLS. 


venience  will  permit.  An  inspection  of  Fig.  495  shows  the 
reason  for  this.  If  the  portion  D  E  F  G  of  the  work  is  to  be 
removed  by  the  cutter,  it  is  evident  that  the  smaller  cutter  X 


will  travel  the  distance  B  in  completing  the  cut,  while  the  cutter 
Y  must  travel  the  distance  A.  If  the  width  W  of  the  work  is 
small,  the  saving  in  time  required  for  the  work  by  using  the 
small  cutter  becomes  a  considerable  portion  of  the  total  time. 


MILLING    MACHINE    WORK. 


36i 


The  first  cost  of  the  smaller  cutter  is  less  and  the  power  required 
to  drive  it  also  less  than  with  the  large  cutter. 

In  placing  cutters  on  the  arbor,  the  faces  of  the  cutter  and 
the  arbor  collars  should  be  carefully  wiped  and  thus  insure  a 
true  running  cutter.  As  shown  in  Fig.  496,  a  small  piece  of 
cutting  or  dirt  A  between  the  faces,  causes  a  spring  in  the 
arbor  and  the  cutter  will  run  out  of  true.  When  made,  the 
faces  of  these  collars  are  carefully  brought  parallel  with  each 
other  and,  with  reasonable  care,  they  can  be  kept  in  this  condi- 
tion. When,  as  in  2  and  3,  Fig.  494,  two  cutters  are  to  be 
used  for  straddle  \vork,  it  is  necessary  when  the  distance  between 


FIG.  495. 


FIG.  496. 

the  faces  of  the  work  is  to  be  of  exact  dimension,  to  have  collars 
of  suitable  length.  As  the  regular  collars  usually  make  up  by 
eighths  above  one-fourth  inch,  suitable  washers  must  be  pro- 
vided for  making  up  the  exact  dimension.  These  may  be  had 
with  parallel  faces  and  varying  in  thickness  by  .001 -inch,  thus 
making  it  possible  to  obtain  any  desired  dimension  between  the 
faces  of  the  cutters.  W'hen  it  is  required  to  machine  the  top 
surface  of  the  work,  a  plain  axial  cutter  can  be  used  between 
the  straddle  mills  in  place  of  the  collars  and  washers. 

At  4,  Fig.  494,  is  shown  the  final  operation  in  the  milling  of 
a  T-slot.     The  neck  of  the  slot  and  all  the  metal  possible  should 


362 


MODERN    MACHINE    SHOP    TOOLS. 


be  first  removed  with  a  plain  axial  cutter,  as  in  Fig.  497,  which 
leaves  a  minimum  amount  of  work  for  the  more  delicate  T-slot 
cutter  to  perform.  If  the  nature  of  the  work  is  such  that  a 
plain  cutter  cannot  be  used,  the  stock  can  be  removed  with  an 
end  mill.  In  this  case,  a  cutter  somewhat  smaller  in  diameter 
than  the  required  width  of  the  neck  must  be  used  first,  as  the 
spring  of  so  small  a  cutter  when  taking  such  a  heavy  cut  would 
cause  the  work  to  be  untrue.  The  neck  can  then  be  finished  to 
exact  width  by  passing  a  sizing  cutter  through  or  by  trimming 
each  side  with  a  finishing  cut  with  the  roughing  cutter.  The  mill- 
ing of  a  V-slot,  5,  Fig.  494,  is  similar  to  that  of  the  T-slot,  the 
most  of  the  stock  preferably  being  first  removed  with  a  plain 
cutter  or  an  end  mill.  The  cutter  shown  could  be  used  to  com- 
plete the  work  at  once,  without  the  use  of  a  stocking  cutter  as 
it  is  provided  with  teeth  on  its  shank.  This  is  not,  however,  the 


FIG.  497. 


PIG.  498. 


FIG.  499. 


customary  method,  as  the  necks  of  these  cutters  are  not  usually 
provided  with  teeth  and  the  spring  of  the  cutter  makes  smooth, 
accurate  results  very  hard  to  obtain. 

At  6,  Fig.  494,  is  illustrated  a  method  of  milling  the  guides 
of  a  housing.  With  a  cutter  of  proper  thickness  and  diameter, 
both  sides  and  bottom  of  the  guides  are  finished  at  one  cut. 
This  figure  serves  to  suggest  one  of  many  similar  operations 
that  can  be  performed  with  a  plain  cutter.  No.  7,  Fig.  494, 
shows  how  the  milling  machine  can  be  used  for  boring  and 
facing  work.  The  work  is  clamped  to  the  table  of  the  machine 
and  a  short  boring  bar  placed  in  the  spindle  bearing.  If  the 
hole  to  be  bored  is  of  considerable  length  and  diameter,  the 
outer  end  of  the  bar  should  be  formed  to  fit  the  bearing  of  the 
overhanging  arm,  thus  making  it  firm  and  capable  of  producing 
a  smooth,  true  bore.  An  automatic  in-and-out  feed  is  very  de- 
sirable for  work  of  this  character.  It  will  also  be  noted  that  the 


MILLING    MACHINE    WORK.  363 

vertical  and  lateral  adjustments  to  the  work  table  enable  the  work 
to  be  set  in  any  desired  position  for  the  boring  of  parallel  holes. 
Take,  for  example,  the  piece  of  work  shown  in  Fig.  498,  where 
the  two  holes  are  to  be  bored  parallel  with  each  other.  The 
work  should  be  first  squared  up  and  the  hole  A  bored;  after 
which,  by  means  of  the  graduated  elevating  screw,  the  work  can 
be  dropped  exactly  ij/6  inches  and  by  means  of  the  graduated 
feed  screw  set  over  the  4)4  inches,  which  brings  the  center  of 
the  hole  B  into  exactly  the  proper  position  for  boring.  In  like 
manner  any  desired  number  of  settings  may  be  obtained  quickly 
and  with  great  accuracy.  In  making  setting  measurements  by 
the  use  of  the  graduated  screws  precaution  must  be  taken  to 
avoid  the  error  that  might  arise  from  neglecting  to  consider  the 
back  lash  between  the  screw  and  its  nut.  Thus,  if  a  vertical  ad- 
justment is  to  be  made,  the  table  for  the  first  operation  should 
be  dropped  a  little  too  low  and  brought  up  to  the  proper  point. 
The  index  can  then  be  set  at  zero  and  the  work  table  raised  the 
exact  amount  required  by  the  graduated  screw.  If  by  accident 
the  table  is  raised  too  high,  it  should  be  lowered  somewhat  below 
the  proper  point  and  again  brought  up  to  the  correct  reading. 
This  insures  against  any  error  arising  from  the  back  lash  and 
means  that  in  all  settings  the  slack  between  the  nut  and  screw 
should  be  kept  on  the  same  side. 

A  long  tool  with  cutting  edge  at  right  angles  to  the  boring 
bar  may  be  used  for  facing  off  the  end  of  the  work  after  the 
boring  operation.  The  end  next  to  the  spindle  can,  of  course, 
be  faced  with  an  end  mill  if  desired,  or  a  facing  attachment  con- 
sisting of  a  slide  and  tool-carrying  head  can  be  mounted  for 
this  purpose  on  the  nose  of  the  spindle  or  on  the  boring  bar. 
Twist  drills  and  reamers  mounted  in  the  spindle  of  the  milling 
machine  can  frequently  be  used  to  very  good  advantage  on 
many  classes  of  work. 

No.  8,  Fig.  494,  shows  the  method  of  keyseating  a  shaft  in 
the  milling  machine.  Where  the  keyway  is  not  cut  the  entire 
length  of  the  work,  a  rounded  end  is  left,  which  is  usually  not 
objectionable.  If  a  cutter  of  small  diameter  is  used  the  length 
of  the  rounded  end  is  not  great.  In  cases  where  the  keyway 
must  be  full  depth  to  the  end,  an  end  mill  of  diameter  equal 
to  the  width  of  the  keyway  can  be  used  to  finish  out  the  rounded 
end.  By  placing  several  shafts  together  on  the  table  and  putting 
as  many  cutters  on  the  arbor,  properly  spaced,  all  keyways  may 


364 


MODERN    MACHINE    SHOP    TOOLS. 


be  cut  at  one  operation.  This  is  advantageous  where  a  large 
number  are  to  be  cut  at  one  setting  of  the  machine.  When  a 
keyway  is  to  be  cut  in  the  shaft  at  some  point  between  the  ends, 
to  receive  a  short  key  or  feather,  the  end  mill  is  used.  If  the 
mill  is  not  of  the  center-cut  type  a  small  hole,  a  little  larger  than 
the  diameter  of  the  toothless  center  of  the  cutter,  should  be 
drilled  at  one  end  and  to  a  depth  equal  to  the  depth  of  the  re- 
quired keyway.  This  allows  the  mill  to  cut  its  way  to  the  bottom 
and  then  feed  out.  For  this  work  the  cutter  should  run  at  a 


FIG.  500. 

comparatively  high  rotative  speed  and  should  be  given  a  fine 
feed,  as  otherwise  the  spring  is  excessive  and  the  work  untrue. 
No.  9,  Fig.  494,  shows  the  method  of  fluting  a  reamer.  The 
present  example  is  that  of  a  taper  reamer.  In  this  case  the  tail 
center  is  raised  an  amount  sufficient  to  give  the  proper  depth  of 
cut  at  each  end  of  the  flutes.  The  cutters  usually  employed  for 
this  work  are  specially  formed  cutters  and  should  be  set  so  that 
the  face  of  the  cutter  that  cuts  the  front  face  of  the  tooth  stands 
on  a  radial  line  with  the  blank  being  fluted,  as  shown  in  Fig.  499. 


MILLING    MACHINE    WORK.  365 

No.  10,  Fig.  494,  shows  the  method  of  cutting  spur  gears 
in  the  plain  or  universal  milling  machine.  One  or  more  of  the 
gear  blanks  are  mounted  on  a  mandrel  and  placed  between  the 
centers,  the  gear  cutter  having  been  previously  placed  on  the 
arbor  and  the  table  adjusted  in  and  out  so  the  center  of  the 
cutter  falls  in  the  line  of  the  work  centers.  The  index  is  set  to 
give  the  correct  number  of  divisions  and  the  work  elevated  until 
the  rotating  cutter  just  touches  the  rim  of  the  gear  blank.  The 
graduated  dial  on  the  elevating  screw  is  then  set  to  zero,  the 
work  moved  out  from  under  the  cutter  and  raised  an  amount 
equal  to  the  required  depth  of  the  tooth.  Spur  gears  too  large 
to  swing  between  centers  can  often  be  cut  by  placing  the  index 
head  spindle  in  a  vertical  position  and  carrying  the  blank  on  a 
vertical  mandrel  held  in  the  spindle.  This  places  the  blank  in 
a  horizontal  plane  and  the  cutter  is  set  to  depth  by  the  table 
feed  screw  and  the  work  fed  to  the  cutter  by  the  vertical  feed. 

In  Fig.  500  is  shown  a  method  of  cutting  a  large  spur  gear  in 
a  plain  milling  machine  using  a  plain  dividing  head  clamped  to 
a  knee  plate.  The  gear  shown  is  30  inches  in  diameter.  The 
greatest  care  must  be  taken  in  an  operation  of  this  kind  as  the 
leverage  on  the  spindle  of  the  dividing  head  is  considerable  and 
the  chances  of  shifting  the  work  great,  especially  if  the  cutter 
is  a  little  dull.  By  previously  gashing  the  work  with  a  plain  cut- 
ter, the  chances  for  a  true  job  are  very  materially  improved. 

Another  method  of  cutting  large  spur  gears  in  the  milling 
machine  is  illustrated  in  Fig.  501.  This  is  known  as  .the  under 
cutting  method  which  is  accomplished  by  raising  the  dividing 
head  and  tail  stock  by  means  of  suitable  elevating  blocks  and 
providing  a  substantial  outer  support  for  the  milling  arbor.  An 
adjustable  post  in  the  tail  stock  raising  block  can  be  brought  to 
bear  against  the  rim  of  the  blank  immediately  over  the  cutter, 
thus  taking  the  cutter  thrust  and  relieving  the  centers  of  this 
strain. 

The  fluting  of  the  tap  shown  at  No.  n  is  similar  in  all 
respects  to  the  fluting  of  the  reamer  in  No.  9.  No.  12  shows  the 
method  of  hobbing  a  worm  gear,  the  blank  having  been  pre- 
viously gashed.  The  hob  is  a  cutter  of  exactly  the  same  shape 
as  the  worm  that  is  to  mesh  with  the  gear  and  simply  forms  out 
the  teeth,  the  blank  rotating  free  on  the  centers.  In  gashing  the 
teeth  of  the  worm  gear  before  hobbing,  it  is  placed  on  the  man- 
drel between  centers  and  the  index  set  for  the  proper  number  of 


366 


MODERN    MACHINE    SHOP    TOOLS. 


teeth.  A  gear  cutter  of  suitable  size  to  remove  most  of  the  stock, 
leaving  only  enough  for  the  hob  to  finish,  is  placed  on  the  arbor 
and  brought  central  with  the  work.  It  is  then  necessary  to  swivel 
the  table  an  amount  C  D  E,  Fig.  502,  depending  upon  the  pitch 
and  diameter  of  the  worm.  The  work  is  then  raised  to  the  cut- 
ter the  proper  amount  and  dropped  for  each  succeeding  cut. 
If  the  thread  of  the  worm  wheel  is  to  be  ri^ht-handed,  the  table  is 


FIG.  501. 

swiveled  to  the  right,  and  to  the  left  if  left-handed.    For  the  hob- 
bing,  the  bed  is  set  back  to  zero. 

Bevel  and  miter  gears  may  be  cut  in  either  the  plain  or  uni- 
versal milling  machines  when  equipped  with  an  elevating  index 
head.  The  teeth  so  cut  are  of  approximate  outline,  but  suffi- 
ciently exact  for  all  ordinary  uses.  As  shown  in  Fig.  503,  the 
gear  blank  is  mounted  on  a  suitable  mandrel  held  in  the  chuck 
or,  as  shown,  fitted  to  the  spindle  bearing  of  the  elevating  head. 
The  head  is  then  elevated  until  the  root  line  of  the  tooth  is 


MILLING    MACHINE    WORK. 


367 


parallel  with  the  work  table.     The  proper  cutter  for  the  particu- 
lar pitch   and   number   of  teeth   is   placed   on   the   cutter   arbor 
and   brought   central   with  the   work. 
For   any   pitch   the   depth   and   width 
at  the  outer  end  of  the  tooth  is  the 
same  as  for  spur  gears.     As  the  inner 
end  of  the  space  is  narrower,  the  cut-         c 
ters  for  bevel  gears  must  be  thinner     --g" 
than  for  spur  gears.     The  index  hav- 
ing been   set   for  the  proper  number 
of  teeth  a  few  center  cuts  are  taken. 
The  index  pin  is  then  advanced  a  few 
holes  and  the  work  moved  out  a  few 
thousandths  from  the  central  position  FIG-  5°2- 

and  the  cutter  again  passed  through 

the  spaces  already  cut.     This  should  remove  some  of  the  stock 
from  the  side  of  the  teeth,  taking  more  at  the  outer  end  than  at 


FIG.  503. 

the  inner  end.     The  index  pin  is  next  carried  back  double  the 
number  of  holes  it  was  advanced  and  the  work  moved  in  double 


368  MODERN    MACHINE    SHOP   TOOLS. 

the  amount  it  had  been  moved  out  for  the  previous  cut.  This 
throws  the  cut  on  the  opposite  side  of  the  tooth.  As  there  is  no 
fixed  rule  for  the  amount  of  these  settings,  the  tooth  must  be 
measured  and  if  not  of  proper  thickness  another  trial  setting  must 
be  taken.  When  the  proper  settings  are  found  for  any  particular 
gear,  they  should  be  noted  for  future  reference.  The  center  cut 
is  then  not  necessary  as  the  tooth  is  finished  by  the  two  side  cuts. 
In  Fig.  504  is  shown  a  method  of  cutting  bevel  gears  in  a 
plain  milling  machine  using  a  plain  dividing  head.  A  spline 
is  milled  in  the  face  of  the  knee  plate  at  the  proper  angle  to 


PIG.  504. 

receive  the  tongues  in  the  base  of  the  head  thus  fixing  the 
cutting  angle.  A  separate  spline  must  be  provided  for  each 
angle  of  gear  cut.  When  a  large  variety  of  gears,  necessitating 
a  number  of  different  angles,  are  to  be  cut  a  plain  graduated 
plate  pivoted  to  the  face  of  the  knee  plate  and  carrying  the 
dividing  head  gives  all  angles.  Where  a  graduated  swivel  base 
vise,  as  shown  in  Fig.  451,  is  available,  it  can  be  used  to  excel- 
lent advantage  in  cutting  the  splines  in  the  knee  plate  at  the  re- 
quired angle. 

The  method  of  cutting  a  twist  drill  in  the  universal  milling 
machine  is  illustrated  in  Fig.  505.  The  settings  are  as  for 
cutting  a  spiral  gear,  with  this  difference,  that  the  depth  of 


MILLING    MACHINE    WORK. 


369 


the  flute  in  a  twist  drill  should  be  less  at  the  shank  end  than 
at  the  point.  It  is  therefore  necessary  to  elevate  the  point  some- 
what. When  the  flute  is  to  be  cut  from  the  very  end  of  the 
blank,  the  shank  must  be  held  in  a  chuck  on  the  spindle  of  the 


FIG/505. 

universal  head,  and  for  the  outer  end,  supported  on  a  suitable 
steady  rest.  If,  however,  the  work  can  be  carried  on  centers 
and  the  cutter  dropped  into  its  cut  as  close  to  the  point  as  pos- 
sible, better  results  can  usually  be  obtained  with  less  liability  to 
accident.  In  this  case,  the  head  spindle  can  be  dropped  a  few 


J 


FIG.  506. 

degrees  below  the  horizontal  position,  or  the  tail  center  raised 
to  give  the  proper  taper  to  the  web  of  the  drill.  The  backing 
off  of  the  lands  of  the  drill,  as  shown  in  Fig.  506,  is  a  somewhat 
difficult  operation,  requiring  good  judgment  on  the  part  of  the 


370 


MODERN    MACHINE    SHOP   TOOLS. 


operator.  The  work  table  is  swung  through  a  small  angle  indi- 
cated by  the  line  r  a,  which  causes  the  end  mill  to  cut  deeper  at 
c  than  at  e,  thus  clearing  the  lip,  as  shown  in  the  end  view. 


FIG.  507. 


507,  508  and  509  show  examples  of  vertical  milling 
machine  work.  In  Fig.  507  the  end  mill  in  the  vertical  spindle 
is  machining  spots  on  the  inside  surface  of  a  feed  bracket  cast- 


MJLLlNi;    MACIIIXK    WORK. 


371 


ing.  While  this  work,  if  clamped  against  a  knee  plate,  could 
he  done  in  a  horizontal  spindle  machine  with  the  same  cutter, 
it  would  be  much  harder  to  hold  and  more  difficult  to  get  at  for 
settings,  measurements,  etc.  In  Fig.  508,  a'n  angular  cutter  is 
shown,  finishing  the  bevel  face  of  a  round  casting,  secured  to  a 
circular  milling  attachment.  This  work  is  done  very  rapidly  and 
the  same  cutter  is  used  to  mill  the  internal  face  of  the  correspond- 
ing ring  shown  on  the  work  table. 

Frequently  where  duplicate  work  is  held  in  the  vise  and  its 
nature  will   permit,   two  vises   placed   side  by  side  will   greatly 


FIG.  509. 


increase  the   output   of  the   milling   machine,   as   the   work   can 
be  set  up  in  one,  while  being  machined  in  the  other. 

A  large  portion  of  the  work  done  in  a  milling  machine  is 
held  in  the  vise.  Plain  base  vises  as  shown  in  Fig.  450  are 
provided  with  tongues  which  fit  the  wards  in  the  work  table  and 
insure  correct  settings  of  the  vise  jaws,  either  parallel  with  or 
at  right  angles  to  the  cutter  arbor.  With  swivel  base  vises  a 
graduation  is  usually  applied  with  the  zeros  coincident  when 
the  jaws  are  parallel  with  the  cutter  arbor.  To  test  the  correct- 
ness of  the  zero  setting,  remove  the  collars  on  the  arbor  and 
move  the  table  so  as  to  bring  the  upper  edge  of  the  jaw  at  the 
height  of  the  center  of  the  arbor.  Move  the  table  longitudinally 


3/2 


MODERN    MACHINE    SHOP    TOOLS. 


until  the  jaw  touches  the  arbor.  If  the  contact  is  uniform  the 
full  length  of  the  jaw,  the  setting  is  correct.  This  pre-supposes 
a  true  running  arbor.  Squaring  from  the  front  face  of  the 
column  with  an  accurate  square  is  equally  satisfactory  and  the 
better  method  if  the  arbor  is  not  dead  true.  For  the  90  degree 
position  square  the  jaw  from  the  arbor. 

Vise  jaws  are  nicely  finished  and  made  of  hard  or  soft  steel, 
the  hard  jaws  being  most  used.  They  are  so  secured  that  they 
may  readily  be  removed  and  special  jaws  applied  in  their  place. 
The  faces  are  at  right  angles  to  the  work  table,  which  insures 
the  milling  of  the  top  surface  of  work  at  right  angles  with  its 
sides  when  clamped  squarely  in  the  jaws. 

For  the  holding  of  round  work  a  special  V  jaw  as  shown 


FIG.  510. 

in  Fig.  510  is  well  suited.  This  gives  a  three  line  contact  be- 
tween work  and  jaws  and  prevents  the  work  from  tipping  up 
or  down.  It  also  insures,  on  work  of  equal  diameter,  the  same 
height  of  setting,  a  very  important  condition,  which  is  difficult 
to  obtain  with  certainty  when  the  work  is  allowed  to  rest  on  the 
face  of  the  vise  slide,  or  on  a  parallel.  For  much  special  work, 
false  vise  jaws  can  be  used  to  very  excellent  advantage  as  they 
may  be  formed  to  irregular  contours  of  either  work  or  cutter. 
In  Fig.  511  is  shown  an  example  of  heavy  gang  milling.  In 
this  case  the  seats  for  caps  and  quarter  box  cheaks  are  finished 
at  once  through.  It  involves  the  finishing  of  five  horizontal 
and  three  vertical  surfaces.  The  gang  is  made  up  of  four  stand- 
ard cutters  and  one  special  inserted  tooth  cutter.  The  diameter 


MILLING    MACHINE    WORK. 


373 


of  the  large  cutter  determines  the  rotative  speed  for  the  gang. 
On  entering  and  leaving  the  cut  a  coarser  feed  can  he  employed 
than  through  the  middle  of  the  cut. 

The  advantages  of  milling  this  piece  of  work  over  planing  it? 


FIG.  511. 


lie  in  the  possibilities  for  perfect  duplication  in  the  former,  as 
well  as  the  time  saving  element,  it  being  milled  in  approximately 
one-third  the  time  required  for  planing. 

In  Fig.  512,  is  shown  the  stock,  false  vise  jaws  in  which  it  is 


-     FIG.  512. 

held  and  gang  of  cutters  for  the  finishing  the  tool  steel  piece 
shown.  The  stock  has  had  a  screw  machine  operation  upon  it 
before  coming  to  the  milling  machine.  A  suitable  stop  on  one  of 


374 


MODERN     MACHINE    SHOP    TOOLS. 


the  jaws  locates  the  work  in  the  vise  with  reference  to  the  turned 
shoulder.  The  jaws  are  hardened  with  roughed  surfaces  for 
firmly  gripping  the  stock,  and  a  copious  supply  of  lubricant  is 
used  on  the  work  and  cutter.  As  the  cut  is  very  long  and  heavy 
for  the  size  of  the  stock,  J/£  inch  square,  it  must  be  very  firmly 
held  and  a  fine  feed  employed. 

In  Fig.  513  is  illustrated  an  example  of  jig  milling.     In  this 


FIG.  513. 

case  the  jig  consists  of  a  plate  secured  to  the  work  table  of  the 
machine  and  a  second  plate  pivoted  to  it.  The  work  which  has 
been  previously  bored  and  faced  on  its  lower  side  fits  over  a 
projection  on  the  upper  plate  which  holds  it  concentric  with  the 
pivot.  The  work  is  squared  up  and  the  face  mill  machines  one 
of  the  spots.  The  work  is  then  rotated  through  90  degrees,  deter- 
mined by  a  pair  of  stop  pins,  and  the  second  spot  machined.  The 
pair  of  straddle  mills  shown  are  next  used  to  face  off  the  ends 


MILLING    MACHINE    WORK. 


375 


of  the  hub  of  the  upright  part.  It  is  possible  in  this  way  to 
machine  any  number  of  pieces  and  have  them  all  alike. 

The  methods  for  securing  work  to  the  table  of  the  milling 
machine  are  quite  similar  to  those  used  on  the  planer.  The  same 
bolts,  clamps  and  blocking  being  equally  suited  in  both  cases. 
It  is  ordinarily  necessary  to  clamp  the  work  quite  securely  as 
the  tendency  to  shift  under  heavy  cuts  is  great.  As  milling  ma- 
chine tables  are  not  ordinarily  provided  with  holes  for  stop 
pins,  it  is  frequently  necessary  to  bolt  suitable  stops  to  the  table. 
A  bar  laid  crosswise  on  the  table  and  held  with  bolts  in  two  or 
more  of  the  T-slots  makes  an  "excellent  stop.  Round  true  iron 
washers  bolted  to  the  table  may  also  serve  as  suitable  stops. 

Bars  of  cast  iron  planed  true  and  having  tongues  on  the  bot- 
tom side  to  fit  in  the  wards  of  the  table  will  be  found  very  con- 


KIG.  514. 

venient  for  much  work  that  requires  two  surfaces  to  be  milled 
parallel  with  each  other.  Such  a  bar  is  shown  in  end  view  in  Fig. 
514.  They  are  simply  used  for  setting  the  edge  of  the  work 
against  serving  as  a  stop  and  insuring  quick  and  accurate  align- 
ment. By  making  a  casting  in  the  form  of  a  right  angle  triangle 
with  tongues  on  one  edge,  a  very  satisfactory  cross  table  stop  is 
formed  for  milling  surfaces  at  right  angles  to  each  other. 

The  knee  plate  is  much  used  for  holding  work  on  the  mill- 
ing machine,  and  especially  in  the  case  of  special  work  where  a 
plate  serves  as  a  jig.  It  should  be  provided  with  tongues  for 
properly  lining  it  on  the  table,  and  when  used  for  general 
work  the  upright  arm  should  have  a  goodly  number  of  slots  or 
holes  for  receiving  the  clamp  bolts. 

Chuck  work  should  be  kept  as  close  up  to  the  jaws  as  possi- 
ble, thus  making  it  rigid.  When  it  is  necessary  to  operate  on  a 


376 


MODERN    MACHINE    SHOP    TOOLS. 


part  of  chucked  work  extending  far  out  from  the  chuck  jaws, 
it  should  be  supported  in  some  manner.  A  small  adjustable 
center  rest,  usually  furnished  with  universal  machines  or  a 
small  jack  screw  may  be  brought  to  bear  immediately  under  that 
part  of  the  work  the  cutter  is  to  operate  upon.  With  long  work 
held  between  centers  this  support  is  also  valuable. 

In  universal  machines,  taper  milling  may  be  accomplished 
with  work  between  centers,  as  shown  at  9,  Fig.  494,  by  either 
raising  the  tail  center  or  depressing  the  head  center.  As  this 
throws  the  centers  out  of  line,  the  rotation  of  the  work  causes 
the  dog  driving  it  to  move  in  and  out  through  the  face  plate. 
This  is  overcome  by  the  use  of  the  new  dog  and  face  plate 


FIG.  515. 

carrier  shown  in  Fig.  515.  When  the  work  is  held  in  the  chuck 
it  is  necessary  that  the  adjustment  of  head  spindle  be  such  that 
its  center  and  the  center  line  of  the  work  remain  in  the  same  line, 
and  point  directly  toward  the  tail  center,  as  shown  in  Fig.  516. 
Although  the  milling  of  cams  is  usually  performed  on  a 
special  cam  cutting  attachment,  they  may  frequently  be  milled 
in  a  plain  or  universal  head,  using  an  end  mill  as  shown  in  Fig. 
5i6A.  From  the  round  disk  shown  in  the  chuck,  which  is  of  a 
thickness  somewhat  less  than  the  diameter  of  the  cutter  and 
having  a  hub  upon  which  the  chuck  jaws  grip,  the  cam  outline 
shown  by  the  dotted  lines  is  milled.  As  shown,  the  center  of  the 
mill  is  central  with  th'e  disk.  For  the  first  or  roughing  cut, 
raise  the  table  until  the  lower  side  of  the  cutter  reaches  the 


MILLING    MACHINE    WORK. 


377 


center  line  a  a  of  the  work.  This  roughs  down  one  of  the 
straight  sides  of  the  cam.  Next  rotate  the  chuck  slowly  by  means 
of  the  worm  and  gear  until  the  cutter  has  roughed  all  the  sur- 
face around  to  the  point  b.  By  next  dropping  the  work,  the  other 


FIG.  516. 

straight  side  is  milled.  As  machined  the  two  straight  sides  will 
be  flat  but  the  circular  portion  will  be  somewhat  concave,  due  to 
the  high  position  of  the  cutter.  For  the  finishing  cut  the  cutter 
should  be  set  with  its  center  at  the  height  of  the  work  center. 


FIG.  5l6A. 

This  brings  all  of  the  work  on  the  end  of  the  cutter  which 
leaves  a  straight  surface,  but  does  not  cut  as  freely  as  when  set 
for  roughing.  This  class  of  work  brings  considerable  strain  and 
wear  on  the  worm  and  gear  of  the  dividing  head. 


3/8  MODERN    MACHINE    SHOP    TOOLS. 

Cutter  vibration  can  usually  be  traced  to  some  slack  in  table 
joints  or  spindle  bearings.  Heavy  cuts  on  frail  work  are  apt  to 
chatter.  Straight  cutter  teeth  are  much  more  apt  to  cause  chatter 
than  spiral  ones.  A  harmonic  relation  between  the  numbers  of 
teeth  in  the  back  gears  and  the  number  in  the  cutter,  when  the 
machine  is  running  in  back  gear,  is  without  doubt  a  frequent 
cause  of  chattering. 

The  graduated  dials  on  all  table  feed  screws  are  of  great 
value  in  setting  cutters  in  the  proper  position  relative  to  the 
work.  They  should,  when  possible,  be  used  for  making  these 
settings,  care  always  being  exercised  in  taking  up  the  slack  or 
back  lash  in  the  screws. 

In  the  milling  of  steel  and  wrought  iron  a  cutter  lubricant 
is  used.  Lard  oil  is  generally  considered  the  best  for  this  pur- 
pose, although  its  high  cost  often  precludes  its  use  some  form  of 
compound  being  substituted.  Many  of  the  soap  and  soda  com- 
pounds are  very  good  substitutes.  The  object  of  lubrication 
is  to  supply,  not  only  enough  of  the  lubricant  to  keep  down 
friction,  but  enough  to  carry  away  the  heat  of  friction  and  thus 
preserve  the  cutting  edges  and  make  possible  higher  cutting 
speeds.  .Cast  iron  and  brass  do  not  require  a  lubricant. 

Castings  that  are  to  be  milled  should  be  free  from  sand  and 
hard,  flinty  spots.  It  is  desirable  to  pickle  them  and  in  the 
case  of  small  castings,  which  are  very  apt  to  be  hard,  to  anneal 
them.  These  operations  are  inexpensive  and  rapid  and  will  save 
many  cutters  and  much  grinding. 


CHAPTER    XXVI. 

GEAR    CUTTERS    AND    GEAR    CUTTING. 

In  the  cutting  or  forming  of  gear-teeth  two  systems,  known 
as  the  "duplication"  and  the  "generation"  systems,  are  em- 
ployed. 

The  "duplication"  system  is  the  one  most  commonly  employed 
and  may  be  divided  into  two  separate  and  distinct  classes  known 
as  duplication  by  formed  cutters  and  duplication  by  the  templet- 


planing  process.  Duplication  by  formed  cutters  is  the  more  com- 
mon method  and  the  one  with  which  most  shop  men  are  familiar. 
It  involves  the  cutting  of  the  tooth  space  with  a  rotating  or  re- 
ciprocating cutter,  the  side  of  the  tooth  of  which,  has  a  formed 
outline  which  is  a  negative  of  the  side  of  the  tooth  outline  re- 
quired. The  accuracy  of  the  tooth  form  is  therefore  dependent 
on  the  accuracy  of  the  cutter's  outline  and  .theoretically  a  differ- 
ent form  of  cutter  should  be  used  for  each  number  of  teeth  cut  in. 
each  pitch. 


MODERN.    MACHINE    SHOP    TOOLS. 


In  the  templet -planing  process  the  sides  of  the  teeth  are  planed 
with  a  pointed  tool,  the  path  of  the  point  being  guided  by  a  tem- 
plet of  the  correct  outline.  This  process  is  much  slower  than  the 
rotating  formed  cutter  method  and  consequently  is  little  used 
for  other  than  the  cutting  of  miter  and  bevel  gears,  to  which 
work  it  is  admirably  adapted.  In  Fig.  517  is  illustrated  the  Glason 
templet  bevel  gear  planer  and  in  Fig.  5I7A  an  outline  of  its  move- 
ments showing  how  it  is  possible  to  make  the  point  of  the  cutting 
tool  duplicate  the  templet  outline  to  a  uniformly  reducing  scale 
from  the  outer  to  the  inner  end  of  the  tooth,  thus  giving  a  correct 
outline  tooth,  its  accuracy  depending  upon  the  accuracy  of  the 
templet.  With  the  formed  cutter  it  is  possible  in  bevel  gear  cut- 


FIG. 


ting  to  give  a  correct  tooth  outline  only  at  one  point  in  the  tooth's 
length.  The  method  is,  however,  much  more  rapid  and  for  the 
finer  pitches  is  much  used.  For  the  coarser  pitches  and  relatively 
longer  teeth,  where  quiet,  smooth  running  gears  are  required,  the 
planing  process  is  used. 

The  generating  of  conjugate  tooth  outlines,  or  in  other  terms, 
the  forming  of  the  teeth  upon  cylinders  that  will  cause  them  to 
roll  together  as  the  pitch  circle  of  the  one  would  roll  upon  the 
pitch  circle  of  the  other  without  slipping,  is  a  condition  that  can 
•only  be  obtained  by  a  molding  process. 

When  two  newly  cut  gears  run  together,  a  molding  process 
takes  place,  the  high  parts  wearing  down  and  gradually  produc- 
ing a  smooth  running  conjugate  tooth.  If  the  teeth  of  one  gear 


GEAR  CUTTERS  AND  GEAR  CUTTING. 


were  covered  with  fine  file-like  teeth  it  would  quickly  mold  the 
teeth  of  the  other  gear. 

The  forming  of  teeth  in  this  manner  by  a  process  known  as 
the  molding-planing  process  has  but  recently  been  put  into  a. 
practical  form  for  spur  gear  cutting  in  the  Fellows  gear  shaper. 

The  single-tooth  molding-planing  process,  as  applied  in  the 
Bilgrim  machine,  generates  conjugate  teeth  on  miter  and  bevel 
gear  blanks. 

The  making  of  formed  gear  cutters  involves  the  laying  out 
of  the  templet  and  making  of  the  negative  cutting  tool  as  described 
in  connection  with  Fig.  472. 

As  the  tooth  outline  varies  with  the  number  of  teeth  in  the 
gear  a  cutter  can  be  made  exactly  correct  for  but  one  number  of 
teeth.  In  practice,  however,  the  outline  varies  so  slightly,  espe- 
cially for  the  larger  numbers  of  teeth,  that  one  cutter,  although 
exactly  correct  for  but  one  number  of  teeth,  is  used  for  cutting 
quite  a  range  of  numbers.  As  the  tooth  outline  changes  very 
rapidly  for  the  lower  numbers  of  teeth  the  range  is  small  for 
these  numbers.  In  the  involute  system  the  permissible  range  is 
much  wider  than  in  the  cycloidal  system.  In  the  following  table 
is  given  the  numbers  and  range  of  Brown  &  Sharpe  involute  gear 
cutters : 

i  will  cut  wheels  from  135  teeth  to  a  rack. 


No. 


55 
35 
26 

21 
17 
14 


134  teeth. 

54  " 
34  " 
25  " 
20  " 
16  " 


(    8  "  .      12  13 

In  cases  where  a  finer  division  is  required  in  the  number  of 
teeth  to  be  cut  with  each  cutter,  as  sometimes  occurs  when  very 
smooth  running  gears  are  required,  intermediate  cutters  between 
those  regularly  used  may  be  had  on  special  order.  The  range  of 
these  cutters  is  given  in  the  following  table : 


No.  of  Cutter. 

Range. 

No.  of  Cutter. 

Range. 

.* 

80  to  134  teeth. 

M 

19 

to  20  teeth. 

21  > 

42  "    54       " 

6^ 

15 

"  16       " 

3* 

30  "    34 

7/2 

13 

4'1'2' 

23  "    25 

MODERN    MACHINE    SHOP    TOOLS. 


In  the  cycloidal  system  24  cutters  are  required  for  cutting  all 
numbers  from  12  teeth  to  a  rack  as  given  in  the  following  table: 

Cutter  M  cuts  27  to  29  teeth. 

N  cuts   30  to  33 

O  cuts   34  to   37 

P  cuts   38  to   42 

Q  cuts   43   to   49 

"        R  cuts    50   to    59      " 

'"        S  cuts   60   to   74      " 

T  cuts   75   to   99 

"        U  cuts  100  to  149      " 

V  cuts  150  to  249 

"       W  cuts  250  or  more. 

"     ,    X  cuts  Rask. 

For  bevel  gear  cutting,  involute  teeth,  eight  cutters  having 
the  same  range  as  above  given  are  required.  These  cutters  differ 
from  those  used  for  spur  gearing  in  that  they  are  considerably 
thinner,  a  condition  made  necessary  by  the  cutters  having  to  pass 
through  the  narrow  end  of  the  tooth  space.  The  regular  bevel 


Cutter 

A 

cuts 

12 

teeth. 

" 

B 

cuts 

13 

" 

" 

C 

cuts 

14 

« 

M 

D 

cuts 

15 

" 

" 

E 

cuts 

16 

" 

« 

F 

cuts 

17 

" 

" 

G 

cuts 

18 

*T'"- 

« 

H 

cuts 

19 

« 

(t 

I 

cuts 

20 

" 

(( 

J 

cuts 

21     tO     22 

" 

(( 

K 

cuts 

23   to   24 

It 

" 

L 

cuts 

25    to    26 

" 

FIG.  518. 

gear  cutters  are  thin  enough  to  pass  through  the  narrow  end  of  the 
space  where  the  length  of  the  tooth  is  not  more  than  1-3  the  dis- 
tance from  the  outer  end  of  the  tooth  to  the  point  at  which  the 
axes  intersect.  Where  an  extra  length  of  tooth  is  required,  an 
especially  thin  cutter  must  be  used. 

Cutters  for  spur  gears  have  the  pitch  and  the  range  of  teeth 
stamped  on  them.  Cutters  for  bevel  gears  have  the  pitch,  but  not 
the  range  stamped  on  them,  inasmuch  as  the  range  does  not  or- 
dinarily correspond  to  that  given  for  spur  gears.  The  selecting  of 


GEAR  CUTTERS  AND  GEAR  CUTTING. 


383 


the  proper  cutter  for  a  spur  gear  is  therefore  a  simple  matter, 
as  it  is  only  necessary  to  know  the  diametral  pitch  and  the  number 
of  teeth.  With  bevel  gears,  however,  the  following  considerations 
are  necessary.  In  any  pair  of  bevel  gears  lay  off  the  back  cone 
radius  a,  b  for  the  gear,  and  b,  c  for  the  pinion,  Fig.  518.  Con- 
sidering the  gear,  r  is  the  actual  pitch  radius  and  upon  which 
the  pitch  and  number  of  teeth  depend.  The  outline  of  the  tooth, 
however,  is  the  same  as  for  a  spur  gear,  having  a  radius  a,  b. 
Take,  for  example,  r  as  equal  to  4  inches,  and  assume  Xo.  6 
diametral  pitch,  which  would  give  48  teeth  in  the  gear,  requiring, 
if  it  was  a  spur  gear,  cutter  No.  3.  The  back  cone  radius  a.  b 
measures  8  inches,  requiring  a  tooth  outline  the  same  as  a  spur 


FIG.  519. 


FIG.    S20. 


gear  of  96  teeth,  or  cutter  Xo.  2,  which  would  be  the  correct  cut- 
ter to  use. 

In  Fig.  519  is  shown  the  Gould  &  Eberhardt  duplex  gang 
gear  cutter,  which  consists  of  two  or  more  cutters  mounted  to- 
gether and  of  such  diameters  and  forms  as  to  cut  and  correctly 
finish  two  or  more  teeth  at  each  passage  through  the  blank.  An 
inspection  of  the  figure  shows  the  central  cutter  to  be  of  normal 
diameter  and  symmetrical  with  reference  to  a  central  plane.  The 
side  cutters  are  somewhat  larger  in  diameter  and  the  center  line 
of  the  front  face  of  each  tooth  is  coincident  with  a  radius  of  the 
blank.  It  is  evident  that  but  one  diameter  of  gear  can  be  cut  with 
each  gang,  and  the  larger  the  diameter  of  the  blank  for  a  given 


384  MODERN    MACHINE    SHOP    TOOLS. 

pitch,  the  more  cutters  it  is  possible  to  mount  in  one  gang. 
This  condition  at  once  makes  the  gang  a  purely  manufacturing 
tool,  which  can  be  advantageously  adapted  only  in  cases  where 
large  numbers  of  each  size  of  gears  are  to  be  cut.  In  using  these 
gangs,  care  must  be  exercised  in  setting  to  the  exact  depth  of  cut 
and  that  the  blanks  are  of  exact  diameter,  as  inaccuracies  in 
these  conditions  will  produce  thick  or  thin  teeth. 

These  cutters  are  ground  from  the  front  face  without  chang- 
ing their  form.  With  these 'gangs  as  many  as  ten  finished  teeth 
may  be  cut  at  one  passage  through  the  blank.  Under  ordinary 
conditions  the  excessive  heat  generated  by  the  removing  of  so 
much  stock  necessitates  a  somewhat  slower  rate  of  feed  and  cutter 
rotation  than  can  be  employed  with  single  cutters.  A  jet  of  com- 
pressed air  directed  against  the  work  and  cutters  makes  possible 
much  higher  speeds. 

The  Clough  duplex  cutter,  as  shown  in  Fig.  520,  although  a 
form  of  gang  cutter,  finishes  but  one  tooth  at  a  time.  The  object 
of  this  cutter  is  to  produce  gears  having  a  widely  different  number 
of  teeth,  that  will  interchange  with  a  single  cutter.  Correct  tooth 
outline  must  of  necessity  be  sacrificed  in  accomplishing  this  end. 
Gears  cut,  however,  with  these  cutters  run  fairly  well  together 
and  will  work  with  gears  cut  with  regular  involute  cutters.  Gears 
having  30  teeth  or  over  are  finished  entirely  by  the  inside  faces  of 
the  cutter.  For  numbers  lower  than  30  the  flanks  are  finished 
by  the  outer  faces  of  the  cutters. 

The  methods  of  cutting  spur  and  bevel  gears  already  described 
in  Chapter  XXV.,  require  the  continuous  attention  of  the  operator 
with  a  constant  danger  of  his  making  an  error  in  division.  Auto- 
matic gear  cutting  machines  insure  better  gear  at  very  much  lower 
cost.  In  Fig.  521  is  shown  an  automatic  gear  cutter  capable  of 
cutting  spur  gears  only  up  to  40  inches  in  diameter  by  9  inches 
face. 

In  Fig.  522  is  styown  an  automatic  gear  cutter  for  cutting  both 
spur  and  bevel  gears  up  to  18  inches  diameter  by  4  inches 
face. 

In  these  machines  all  movements  are  entirely  automatic.  The 
work  is  secured  to  the  dividing  head  spindle  ;  the  necessary  change 
gear  adjustments  made  for  dividing  the  work ;  the  work  set  to  the 
cutter  so  as  to  cut  the  proper  depth  of  tooth,  the  correct  cutter 
having  previously  been  put  on  the  cutter  spindle,  and  the  machine 
started  up.  When  the  feed  is  thrown  in  the  cutter  advances 


GEAR    CUTTERS    AND    GEAR    CUTTING.  385 

through  the  blank  at  the  required  rate  of  feed,  automatically  re- 
versing when  the  cut  has  finished  and  returning  the  cutter  slide 
at  a  quick  speed.  When  the  cutter  on  its  return  stroke  has  cleared 
the  work,  the  dividing  mechanism  spaces  for  the  next  tooth  and 


FIG.  521. 


FIG.  522. 

the  cycle  of  operation  is  again  gone  through,   repeating  itself 
without    further  attention  until  the  work  is  finished. 

For  the  cutting  of  bevel  gears  in  the  automatic  machine  it  is 
necessary  that  the  cutter  slide  be  so  constructed  that  it  can  be  set 


386  MODERN    MACHINE    SHOP   TOOLS. 

at  any  angle  between  a  horizontal  and  a  vertical  position.  As 
with  the  cutting  of  bevel  gear  in  the  milling  machine,  the  cutter 
must  pass  twice  through  each  space,  the  automatic  features  of  the 
machine,  however,  remaining  the  same  as  for  spur  gear  cutting. 

Due  to  their  smoothness  of  action,  spiral  gears  running  in  oil 
are  largely  used  for  driving  the  cutter  spindle.  As  the  center  of 
the  cutter  must,  for  spur  gear  cutting,  be  under  the  center  of  the 
work  and  as  the  cutters  vary  in  thickness,  it  is  necessary  to  give 
the  spindle  an  adjustment  endwise  and  to  provide  a  suitable  gauge 
for  setting  the  cutter  central. 

The  feed  to  the  cutter  slide  on  the  machines  shown  is  accom- 
plished by  a  slow  rotation  of  the  feed  screw,  which  rate  can  be 
varied  within  necessary  limits  by  a  change  of  gearing.  The  auto- 
matic disengaging  by  stops  of  the  clutch,  which  engages  the  for- 
ward driving  gear  with  the  feed  screw,  stops  the  feed.  The  same 
movement  engages  the  screw  with  a  quick-running  reverse  gear 
which  brings  the  slide  back  very  rapidly.  The  changes  from  the 
one  movement  to  the  other  occur  without  pause  or  shock. 

The  exactness  with  which  the  dividing  mechanism  performs 
.its  work  is  dependent  upon  an  accurately  cut  worm  gear  and 
worm ;  accurately  cut  change  gears ;  nicely  fitting  bearings  and 
adjustments  permitting  of  no  back  lash  ;  and  an  escapement  move- 
ment which  allows  the  locking  disc-shaft  to  make  exactly  one 
revolution,  or,  as  is  the  case  with  the  Brown  &  Sharpe  machines, 
two  or  four  revolutions  at  the  time  the  division  is  made.  In  these 
machines  a  side  shaft  rotating  at  a  constant  rate  of  speed  carries 
a  clutch  which  at  the  instant  of  the  tripping  of  the  escapement 
stop  engages  the  locking  disc  causing  it  to  rotate  through  one, 
two,  or  four  revolutions,  depending  on  the  setting.  This  has  the 
advantage  of  reducing  the  number  of  change  gears  necessary. 

Referring  to  Fig.  523,  B  is  the  gear  on  the  locking  shaft,  C 
and  D  are  intermediate  gears  on  a  stud,  and  E  is  the  worm  gear, 
which  transmits  its  motion  to  the  worm  through  a  pair  of  miter 
gears.  The  number  of  teeth  in  the  worm  divided  by  the  number 
of  teeth  to  be  cut,  represents  the  ratio  that  must  be  made  up  by  the 
change  gears.  Thus  if  120  teeth  are  required  the  ratio  is  one, 
and  gears  must  be  selected  that  will  give  this  ratio,  as  B  50,  C  5°> 
D  60,  and  E  60.  If,  for  example,  82  teeth  are  wanted, 
120  60  2  30 

82        41       i        41 


GEAR  CUTTERS  AND  GEAR  CUTTING. 


giving  gear  B  100,  C  50,  D  30,  E  41.  As  a  gear  with  41  teeth  is 
not  available,  60  and  82  may  be  used  on  D  and  E.  If  in  the  latter 
case  41  teeth  were  wanted,  two  revolutions  of  the  locking  disk 
could  be  employed,  using  the  same  change  gears. 

Where  \vork  of  small  diameter  is  operated  upon,  the  outer  end 
of  the  work  mandrel  is  supported  by  an  overhanging  arm  and 
no  further  support  is  necessary.  If  of  large  diameter  the  end  of 
the  mandrel  is  carried  in  an  outboard  support,  and  a  rim  support 
steadies  the  blank  immediately  back  of  the  cutter.  In  setting  the 
work  to  depth  it  should  be  lowered  until  the  revolving  cutter  just 
touches  the  circumference,  and  the  dial  on  the  elevating  screw  then 
set  at  zero.  It  should  then  be  dropped  the  required  amount  for 


FIG.  523. 

the  cut  by  passing  somewhat  beyond  the  required  distance  and 
turning  up  to  the  mark,  thus  avoiding  any  error  due  to  back  lash 
in  screw  and  connections. 

Gear  cutting  machines  when  used  on  steel  gears  are  provided 
with  an  oil  pump  for  supplying  a  liberal  amount  of  screw  cutting 
oil  on  cutter  and  work.  In  the  cutting  of  steel  gears,  when  prop- 
erly lubricated,  a  high  rotative  cutter  speed  with  very  fine  feeds 
are  usually  advisable.  The  lubricant  prevents  the  heating  of  the 
cutter  and  the  fine  feed  overcomes  its  tendency  to  "hog"  into  the 
work. 

The  cutting  of  bevel  gears  in  the  automatic  machine  shown 
in  Fig.  522  does  not  differ  materially  from  the  milling  machine 
method  described  in  connection  with  Fig.  503.  The  side  move- 


388 


MODERN    MACHINE    SHOP    TOOLS. 


ment  is  given  the  cutter  rather  than  the  work,  and  the  same  care 
and  judgment  must  be  exercised  in  making  the  preliminary  set- 
tings. In  the  cutting  of  heavy  pitch  and  steel  bevel  gears,  it  is 
usually  advisable  to  make  a  center  cut,  thus  necessitating  three 
cuts  for  each  tooth. 

The  cutting  of  racks  may  be  accomplished  in  the  milling  ma- 
chine by  use  of  a  special  attachment,  as  shown  in  Fig.  458:  on 
the  automatic  gear  cutter  by  means  of  a  suitable  attachment  or 

& 


FIG.  524. 

on  a  special  automatic  rack  cutting  machine.  An  attachment  for 
the  automatic  gear  cutter  is  shown  in  Fig.  524.  A  cross  rail  is 
secured  to  the  front  of  the  upright,  and  this  is  mounted  on  a  slid- 
ing head  with  provisions  for  clamping  the  rack  blank  on  its  under 
surface.  A  pinion  on  the  nose  of  the  dividing  spindle  engages  a 
rack  on  the  head,  thus  making  it  possible  to  automatically  move 
the  head  the  correct  spacing  for  each  passage  of  the  cutter  through 
the  blank.  Gang  cutters  can  be  advantageously  used  in  rack 
cutting.  All  cutters  must  be  of  exactly  the  same  diameter  and 


GEAR    Cl'TTKRS    AND    C.KAR    CL'TTIXG. 


mounted  on  the  arbor  with  their  centers  the  exact  pitch  distance 
apart.  Where  large  amounts  of  rack  are  to  be  cut,  machines  for 
that  special  class  of  work  are  employed. 

The  Fellows  gear  shaper,  above  referred  to,  is  shown  in  Fig. 
525.  The  cut  illustrates  a  front  view  of  the  machine  at  work  on 
an  internal  gear.  The  cutters  are  illustrated  in  Fig.  526,  and  the 
method  of  securing  them  to  the  cutter  spindle  is  shown  in  Fig. 


FIG.  525. 

527.  As  already  stated  the  cutter  is  a  correctly  formed  gear  dished 
on  the  cutting  face  in  order  to  give  it  an  angle  of  rake.  The  cutter, 
although  resembling  a  spur  gear,  is  in  reality  a  bevel  gear,  having 
a  very  small  center  angle.  This  feature  gives  the  cutter  the  neces- 
sary clearance  in  the  work.  Upon  the  correct  forming  of  the 
cutter  depends  the  accuracy  of  the  work  produced  on  this  machine. 
Since  the  side  of  the  tooth  of  an  involute  rack  is  a  straight  line, 
the  substitution  of  the  face  of  a  cutting  wheel  for  the  side  of  the 


390 


MODERN    MACHINE    SHOP    TOOLS. 


FIG.  526. 


Wbtfc 


FIG.  527. 


GEAR  CUTTERS  AND  GEAR  CUTTING. 


391 


tooth  would  by  the  molding  process  produce  a  correct  involute 
outline  on  the  tooth  of  any  gear  that,  meshing  with  the  rack,  was 
caused  to  pass  this  cutting  face.  Upon  this  fact  is  based  the 
method  by  which  the  Fellows  cutter  is  finished.  The  cutter  hav- 
ing been  planed  from  a  blank,  as  shown  in  Fig.  528,  and  hard- 
ened, is  put  on  a  special  grinding  machine  and  the  tooth  outlines 
ground  to  the  correct  form,  the  operating  of  the  machine  depend- 
ing upon  the  principle  above  explained  and  clearly  illustrated  in 
Fig.  529.  The  rack,  of  which  the  face  of  the  wheel  forms  the  side 
of  one  tooth,  is  a  fixed  imaginary  one  and  the  cutter  blank  is 
given,  by  a  suitable  mechanism,  a  true  rack  and  pinion  motion 


CUTTER 


BLANK 


FIG.  528. 


past  the  face  of  the  emery  wheel,  which  grinds  the  sides  of  the 
teeth,  one  at  a  time,  to  the  correct  form. 

In  its  operation  the  cutter  and  blank  are  so  geared  together 
that  they  rotate  the  same  as  two  complete  gears  in  proper  mesh. 
After  starting  the  machine,  the  cutter  is  fed  toward  the  blank 
until  it  has  cut  the  exactv depth  of  the  tooth.  Rotation  which  cor- 
responds to  a  feed  then  begins,  a  small  amount  at  the  beginning 
of  each  stroke,  when  the  cutter  is  clear  of  the  work  and  continues 
until  the  cutting  is  finished. 

The  method  of  holding  the  work  is  shown  in  Fig.  527,  a  suita- 
ble face-plate  and  clamp  with  a  work  support  in  connection  with 
the  draw  stroke  on  the  cutter  making  a  very  rigid  combination. 
When  the  character  of  the  work  necessitates  it,  the  cut  can  be 


392 


MODERN    MACHINE    SHOP    TOOLS. 


taken  on  the  down  stroke,  such  usually  being  the  case  when 
cutting  internal  gears.  The  stroke  of  the  cutter  ram  is  adjustable, 
as  to  length  and  position. 

Since  the  teeth  of  the  cutter  are  conjugate  to  the  generating 
rack,  all  gears  cut  with  the  cutter  are  conjugate  to  it  and  to  each 
other.  One  cutter  will  therefore  cut  all  gears  from  a  pinion  to  a 
rack. 

Bevel  gears  having  the  octoidal  form  of  teeth  are  cut  theoreti- 


'Emery  Wheel 


Cutter 


FIG.  529. 


cally  correct  by  a  molding  planing  process  in  the  Bilgram  bevel 
gear  planer,  Fig.  530.  The  generating  tool  has  a  straight  cutting 
edge  and  is  given  a  motion  parallel  with  the  root  of  the  tooth  and 
constantly  moving  toward  the  apex  of  the  pitch  cone. 

In  this  machine  the  gear  blank  is  given  a  rolling  motion  as  it 
swings  under  the  cutting  tool.  This  motion  is  accomplished  by 
means  of  a  pair  of  bands  wrapped  about  a  portion  of  a  conical 


GEAR-  CUTTERS    AND    HEAR    CUTTING. 


393 


surface,  having  its  apex  in  the  intersection  of  the  axis,  upon 
which  the  blank  is  mounted  and  the  pivotal  axis  of  the  head.  The 
adjustments  of  the  machine  are  such  that  the  motion  given  the 
blank  is  the  same  as  it  would  receive  if  it  was  rolling  in  gear  with 
a  circular  rack.  As  the  cutting  of  the  tool  corresponds  to  the 
straight  side  of  the  rack  tooth,  its  action  is  to  generate  a  conjugate 
tooth  on  the  blank.  The  indexing  mechanism  spaces  the  teeth 
and  the  feed  rotates  the  blank  slightly  for  each  stroke  of  the  cutter. 
In  the  cutting  of  worm  gears  by  the  hobbing  process  is  illus- 


FIG.  530. 

trated  a  method  of  producing  conjugate  teeth  by  a  rotating  cutter. 
This  operation  as  performed  on  the  universal  milling  machine  is 
described  in  connection  with  12  Fig.  494  and  Fig.  502. 

On  machines  designed  specially  for  hobbing  work  and  known 
as  hobbing  machines,  the  work  spindle  and  hob  are  geared  to- 
gether by  means  of  a  suitable  system  of  change  gears,  thus  driv- 
ing the  work  blank  at  the  proper  speed  relative  to  the  cutter 
rotation.  \Yith  machines  of  this  class  it  is  not  necessary  to  pre- 
pare the  blank  by  gashing,  as  the  gearing  insures  correct  spacing. 
This  method  is  clearly  shown  in  Fig.  531,  which  illustrates  the 
\Yhitney  attachment  for  the  hobbing  of  worm  gears  on  a  plain 


394 


MODERN    MACHINE   SHOP    TOOLS. 


milling  machine.  As  clearly  shown  a  pattern  worm  on  the  work 
.spindle,  having  the  same  number  of  teeth  as  required  on  the  work, 
gears  with  the  hob. 

Spiral  gears  are  usually  cut  in  the  universal  milling  machine 
with  a  formed  disk  cutter  mounted  on  the  regular  cutter  arbor, 
or  preferably  on  the  spindle  of  a  universal  milling  attachment, 
as  shown  in  Fig.  454.  In  the  latter  case  the  setting  for  the 
spiral  angle  is  made  by  swinging  the  auxiliary  cutter  arbor  to  the 
required  angular  position  which  is  a  very  desirable  feature  in 
the  cutting  of  short  pitch  spirals. 

As  is  the  case  with  the  teeth  of  bevel  gears,  spiral  gear  teeth 
can  be  formed  theoretically  correct  by  a  planing  process  in  which 


FIG.  531. 

the  cutting  tool  is  given  a  rolling  feed  that  causes  it  to  follow  the 
outline  of  the  tooth,  the  work  being  rotated  as  it  advances  to  the 
tool  at  the  proper  rate  to  produce  the  required  spiral. 

The  teeth  may  also  be  correctly  formed  by  using  a  planing 
tool  of  the  same  outline  as  the  normal  tooth  space,  the  blank  being 
again  rotated  to  produce  the  proper  spiral.  Teeth  of  spiral  gears 
in  which  the  spiral  angle  is  great,  as  in  a  worm,  are  usually  formed 
by  this  method  in  a  screw  cutting  lathe. 

As  the  planing  process  is  necessarily  an  expensive  one,  the 
more  rapid  yet  less  accurate  method  of  milling  is  usually  used. 
For  this  method  two  forms  of  cutters  are  used,  the  disk  cutter,  the 
same  as  used  for  spur  gear  cutting,  and  the  end  or  shank  cutter. 
Of  these  the  latter  is  used  only  when  cutting  low  numbered  pinions, 


GEAR    CUTTERS    AND    C.EAK    CUTTING.  39  j 

where  the  root  outlines  of  the  teeth  are  so  nearly  parallel  that  a 
disk  cutter  would  clip  oft"  the  teeth  too  much,  thus  making  the  space 
wide  and  the  tooth  thin,  as  well  as  destroying  the  form  of  tooth 
section. 

The  end  cutter  is  given  the  same  shape  as  the  desired  tooth 
space  and  rotates  at  right  angles  to  the  axis  of  the  blank,  both  axes 
being  in  the  same  plane.  The  end  cutter  is  a  delicate  tool  that 
rapidly  loses  its  form  and  does  not  produce  a  spiral  groove  or  tooth 
space  having  exactly  its  outline. 

The  disk  cutter  is  best  suited  to  this  \vork,  as  it  cuts  faster  and 
retains  its  shape  well.  When  made  of  small  diameter  it  can  or- 
dinarily be  used  on  low  numbered  pinions  with  satisfactory  results. 
In  its  use  the  axis  of  the  blank  must  be  placed  at  90  degrees,  minus 
the  spiral  angle,  from  the  cutter  arbor,  the  direction  in  which  the 
angle  is  measured  depending  upon  whether  the  spiral  is  to  be  right 
or  left  handed.  The  blank  as  it  is  fed  to  the  cutter  is  given  the 
proper  rotation  to  produce  the  required  spiral. 

As  the  disk  cutter  operated  in  the  universal  milling  machine 
forms  the  most  practical  method  of  producing  spiral  gears,  we  will 
consider  that  method  of  cutting  in  the  following  examples. 

In  preparing  to  cut  a  spiral  gear  in  the  universal  milling  ma- 
chine the  operator  should  observe  the  following1  points :  Having 
selected  the  proper  cutter  and  secured  it  well  toward  the  outer  end 
of  the  arbor  in  order  to  allow  plenty  of  room  to  swing  the  table 
without  striking  the  housing,  or  upon  the  spindle  of  the  universal 
attachment,  he  will  proceed  as  follows :  First,  move  the  saddle 
until  the  centers  of  the  spindle  and  center  plane  of  the  cutter  coin- 
cide. This  will  bring  the  center  of  the  cutter  over  the  center  about 
which  the  work  table  rotates  in  setting  for  the  spiral  angle. 

Adjust  the  dividing  mechanism  to  give  the  number  of  teeth 
desired  the  same  as  for  spur  gear  cutting  and  release  the  pin  on 
the  back  side  of  the  index  dial  so  that  the  dial  may  rotate  with  the 
worm  spindle. 

The  spindle  must  be  geared  with  the  feed  screw  in  order  to 
obtain  the  required  pitch  of  the  spiral.  A  table  furnished  with 
the  machine  will  give  the  change  gears  to  use  for  a  large  range 
of  pitches.  If  the  pitch  required  does  not  exactly  coincide  with 
any  given  in  the  table,  it  will  usually  be  sufficiently  correct  to  use 
the  one  nearest  the  proper  pitch. 

The  spindle  will  have  right  or  left  hand  rotation,  depending 
on  whether  the  gear  is  to  have  right  or  left  hand  spirals.  The 


396  MODERN    MACHINE    SHOP    TOOLS. 

direction  of  rotation  is  changed  by  driving  through  an  idle  gear 
carried  on  a  second  stud. 

Next  swing  the  table,  or  the  universal  spindle  as  the  case  may 
be,  through  the  spiral  angle  and  elevate  the  knee  until  the  revolving 
cutter  touches  the  circumference  of  the  blank.  Back  the  blank 
from  under  the  cutter  and  again  elevate  the  work,  this  time  an 
amount  equal  to  the  depth  to  be  cut  in  gear.  In  returning,  lower 
the  work  a  little  so  as  to  clear. 


CHAPTER   XXVII. 

DRILLING    MACHINES    AND   DRILLING    WORK. 

Drilling  machines  constitute  a  class  of  machine  tools  which  has 
developed  from  the  lathe.  The  standard  drilling  machine  in  its 
various  forms  consists  primarily  of  a  revolving  spindle  for  carry- 
ing the  cutting  tool ;  a  work  holding  table  and  a  substantial  frame 
connecting  the  two.  The  details  of  spindle  adjustments  and 
spindle  drives  and  feeds*  while  differing  in  points  of  detail  in  the 
several  designs  and  classes,  all  bear  close  mechanical  relations  with 
each  other. 

The  specific  field  for  this  class  of  tools  is  the  drilling  and  boring 
of  holes  of  comparatively  small  diameters.  The  reaming  and  tap- 
ping of  these  holes  are  in  many  cases  added  to  the 'work  of  the 
drill  and  by  means  of  special  tools  and  fixtures  much  work  for- 
merly done  in  the  lathe  is  now  being  performed  on  drilling  ma- 
chines. The  relative  importance  of  this  class  of  tools  in  manufac- 
turing shops  has  been  measured  largely  by  their  ability  to  do 
strictly  drilling  work.  As  a  manufacturing  tool,  it  is,  however, 
due  to  its  simplicity,  the  readiness  with  which  it  can  be  ganged, 
and  its  comparatively  low  cost,  rapidly  growing  in  favor. 

In  Fig.  532  is  shown  a  standard  pattern  upright  drill.  This  is 
a  back  geared  machine,  the  back  gear  mechanism  being  inclosed 
in  the  upper  horizontal  spindle  cone.  This  gives  the  spindle  eight 
speeds.  The  spindle  has  a  three-speed  automatic  feed  with  an 
automatic  stop  for  knocking  the  feed  off  at  any  required  position 
of  the  spindle.  Both  wheel  and  lever  feeds  are  also  provided  with 
a  provision  for  quickly  moving  the  spindle  when  the  worm  on  hand 
wheel  is  disengaged  from  its  gear.  The  rack  and  pinion  method 
of  moving  the  spindle  is  common  to  practically  all  makes  and  styles 
of  drilling  machirre.  The  spindle  has  its  lower  bearing  in  a  quill 
which  is  given  a  close  sliding  fit  in  the  head.  The  feed  rack  is 
secured  to,  the  quill.  The  machine  shown  is  of  the  sliding  head 
pattern,  the  head  having  a  vertical  adjustment  on  the  front  face 
of  the  column  to  adapt  the  machine  to  work  of  different  heights 
and  drills  and  tools  of  varying  lengths.  The  head  is  counter 
weighted  by  an  equivalent  weight  on  the  inside  of  the  column  and 


398 


MODERN    MACHINE    SHOP    TOOLS. 


attached  to  the  head  by  the  chain  shown.     The  head  can  be  firmly 
clamped  in  any  position. 

The  work  table  is  supported  on  an  arm,  which  is  moved  over 
the  column  by  means  of  the  screw  and  crank  shown.  It  can  be 
swung  to  a  considerable  angle  either  side  of  the  spindle  and  firmly 


FIG.  532. 

.lamped  in  any  position.     For  work  too  high  to  be  supported  on 
the  adjustable  table,  the  lower  base  table  is  used. 

On  the  smaller  machines  of  this  class,  a  stationary  head  is  used, 
all  the  vertical  adjustment  being  given  the  table.  Machines  of  this 
general  design  are  regularly  made  up  to  52  inches  capacity,  the 
size  indicating  the  maximum  diameter  of  work,  the  center  of  which 
can  be  reached  by  the  spindle. 

For  driving  small   drills,  a  light  machine  should  be  used  in 


DRILLING    MACHINES    AND    DRILLING    WORK. 


399 


-order  to  obtain  the  high  speed  required  and  the  lightness  of  parts 
necessary  to  make  the  machine  sensitive.  By  the  term  sensitive, 
as  applied  to  small  drilling  machines,  is  commonly  understood  that 
lightness  of  parts,  smooth  running  and  perfect  balance  which 
enables  the  operator  to  judge  as  to  the  pressure  he  is  applying  to 
the  drill  and  consequently  lessen  the  danger  of  drill  breakage. 
In  addition  to  the  above  features  some  builders  go  a  little  farther 
and  employ  at  some  point  in  the  drive  an  adjustable  friction  which 
can  be  so  set  as  to  just  drive  the  drill  being  used. 

In  Fig.  533  is  shown  a  simple  and  efficient  friction  driven  sen- 


.  533- 


FIG.  534. 


sitive  drill.  The  friction  driver  is  adjustable  to  compensate  for 
wear  only.  The  speed  of  the  spindle  is  varied  by  the  position  of 
the  driving  friction  wheel. 

In  Fig.  534  is  shown  an  example  of  a  very  heavy  upright  drill- 
ing machine.  This  machine  is  designed  for  very  heavy  work,  as 
the  boring  and  tapping  of  flanges.  It  is  of  massive  proportions 
and  powerfully  geared. 

When,  as  illustrated  in  Fig.  535,  a  number  of  drilling  spindles 
are  driven  from  one  main  spindle,  the  machine  is  known  as  a  mul- 
tiple spindle  drill.  In  the  drill  shown,  the  spindles  can  be  set  at 
.any  desired  position  within  the  limiting  circle.  This  is  a  manu- 


4OO 


MODERN    MACHINE    SHOP    TOOLS. 


facturing  -tool  adapted  to  the  drilling  of  such  work  as  cylinder 
heads,  chest  covers  or  any  machine  part  where  a  number  of  parallel 
holes  can  be  drilled  at  the  same  time  and  setting.  These  machines 
are  also  made  in  a  horizontal  style  with  one  or  two  heads  for  such 
work,  as  the  drilling  of  cylinder  ends. 

When  several  complete  machines,  each  having  a  single  spindle, 


FIG.  536 

are  mounted  upon  a  common  base  and  driven  either  independently 
or  as  a  single  machine,  they  are  known  as  gang  drills.  They 
possess  many  advantages  and  as  manufacturing  tools  are  coming 
into  quite  general  use. 

In  Fig.  536  is  shown  a  four-spindle  1 4-inch  gang  drill,  which 


DRILLING    MACHINES    AND    DRILLING    WORK.  4O1 

illustrates  favorably  this  class  of  drills  in  the  smaller  sizes.  They 
are  made  with  two  to  eight  spindles  in  this  general  style.  When 
larger  numbers  of  spindles  are  required,  as  for  the  drilling  of  boiler 
plates,  or  bridge  and  structural  work,  the  design  is  materially 
modified,  the  spindle  heads  being  mounted  on  a  cross  rail  which 
is  supported  at  the  ends  by  rigid  housings  resting  on  a  heavy  base 
with  fixed  or  adjustable  work  table. 

With  gang  drills,  as  with  multiples,  the  operating  economy  is 
evident  when  the  work  will  admit  of  their  advantageous  use.  With 
the  gang  drill  when  each  operation  on  the  work  is  short,  a  single 
piece  of  work  is  carried  from  spindle  to  spindle,  but  one  spindle 


FIG.  537. 

working  at  a  time.  The  saving  here  comes  from  not  having  to 
stop  and  start  spindles  and  change  tools.  When  the  length  of 
time  required  for  each  operation  will  permit  the  use  of  the  auto- 
matic feed,  each  spindle  may  be  kept  constantly  at  work,  it  being 
only  necessary  to  stop  it  long  enough  from  time  to  time  to  take  out 
the  finished  piece  and  put  in  another.  When  so  operated  the  tim- 
ing should  be  so  arranged,  if  possible,  that  all  spindles  except  the 
one  at  which  the  work  is  being  changed  are  working. 

The  automatic  feed  and  feed  knock  off  are  quite  necessary  for 
the  latter  class  of  operations. 

When  work  of  large  diameter  is  to  be  drilled  near  its  center, 


402 


MODERN    MACHINE    SHOP    TOOLS. 


the  drilling  spindle  must  be  capable  of  sufficient  radial  adjustment 
to  reach  the  required  point  on  the  work,  hence  the  name  and  class 
radial  drills.  In  Fig.  537  is  shown  a  plain  radial.  The  upright 
or  column  is  carried  on  a  stump,  which  is  securely  bolted  to  the  base 
and  extends  through  the  column.  The  column  rotates  upon  this 
stump  and  can  be  firmly  clamped  to  it  at  any  position.  The  radial 
arm  has  a  vertical  adjustment  by  power  on  the  column,  and  the 
spindle  head  is  radially  adjustable  on  the  arm.  An  extended  base 
receives  heavy  work  and  a  raised  angle  plate  table  the  smaller 
work.  The  drive  is  through  bevel  and  spur  gear  connections  with 
shafts  through  the  center  of  and  down  the  outside  of  the  column, 
along  the  arm  and  up  the  head  to  the  upper  end  of  the  spindle. 
In  the  particular  machine  shown,  a  variable  speed  box,  Fig.  537A, 


FIG.  537A. 


is  substituted  for  the  usual  cone  pulley.  By  means  of  a  lever, 
operating  friction  clutches,  either  of  four  speeds  may  be  instantly 
obtained.  The  back  gear,  which  is  mounted  on  the  butt  of  the 
arm,  is  so  arranged  that  four  speed  changes  are  obtained,  thus 
giving  sixteen  speed  changes  for  the  spindle,  all  of  which  are  ar- 
ranged in  geometrical  progression.  Reversal  of  the  spindle  rota- 
tion for  tapping  is  accomplished  at  the  head,  a  friction  clutch  con- 
trolling same. 

As  the  efficiency  of  a  tool  of  this  class  depends  very  largely 
upon  the  convenience  of  manipulation,  special  attention  to  the 
location  and  arrangement  of  operating  levers  is  given. 

Radial  drills  are  also  made  in  what  are  known  as  "half"  and 
"full"  universal  radial  patterns.  In  the  "half"  universal  radial,  the 


DRILLING    MACHINES    AND    DRILLING    WORK. 


403 


drilling  spindle  is  mounted  on  a  swinging  frame  which  allows  the 
spindle  to  be  set  at  any  angle,  in  a  vertical  plane,  parallel  with  the 
face  of  the  arm.  In  the  "full"  universal  radial  the  arm  is  pivoted 
to  the  butt  in  such  a  manner  that  its  face  can  be  rotated  through 
a  complete  revolution,  thus  making  it  possible  to  drill  holes  at 
any  desired  angle  with  the  base. 

For  a  large  portion  of  the  angular  drilling  work  put  on  these 
machines,   the   universal   drilling  table.    Fig.    538,   in   connection 


with  the  plain  radial  machine,  is  well  suited.  In  this  case  the 
work  rather  than  the  spindle  is  set  at  the  required  angle. 

On  classes  of  work  where  each  operation  is  short,  and  as  a 
consequence  it  is  not  economical  to  attempt  to  work  on  more 
than  one  piece  at  a  time,  turret  head  drills  are  well  adapted.  In 
Fig.  539  is  shown  a  drilling  machine  of  this  class.  The  turret 
carries  a  number  of  spindles  which  can  be  successively  thrown 
into  position.  Each  spindle  carries  its  particular  tool  for  the 
work  in  hand  and  only  the  spindle  in  working  position  revolves. 

In  Fig.  540  is  shown  a  horizontal  spindle  drill  of  radial  pat- 
tern. The  value  of  this  class  of  tool,  not  only  for  general  work, 


404 


MODERN    MACHINE    SHOP    TOOLS. 


but  as  a  manufacturing  drill,  is  not  fully  appreciated.  This  drill 
was  originally  designed  for  the  drilling  and  tapping  of  holes  in 
the  ends  of  long  work.  Its  advantages  for  this  purpose  are 
evident.  For  the  drilling  and  tapping  of  holes  parallel  with  a 
machined  surface,  on  almost  all  classes  of  work  this  machine  is 
superior  to  the  standard  upright  drill,  as  the  work  can  be  more 


FIG.   539. 

readily  set  up  on  the  table  and  without  the  use  of  knee  plates  and 
blockings.  The  machine  is  back  geared  and  provided  with  auto- 
matic power  feed.  Reversal  for  tapping  is  accomplished  by  a 
double  friction  clutch  counter  shaft. 

Post  drills  as  usually  constructed  consist  of  a  substantial 
drilling  head  of  suitable  design  to  permit  its  being  secured  to  a 
post  or  wall. 


DRILLING    MACHINES    AND    DRILLING    WORK. 


405 


Suspension  and  traveling  drills  comprise  a  special  class  used 
for  the  drilling  of  plates  and  other  work  too  large  to  be  handled 
under  a  radial.  The  suspension  drill  is  made  to  bolt  to  the  ceil- 
ing and  the  work  is.  moved  under  it.  With  the  traveling  drill 
the  head  is  mounted  on  a  steel  bridge  which  is  carried  on  side 
tracks  similar  to  a  traveling  crane.  These  machines  have  the 
spindles  motor  driven,  and  although  limited  in  their  vertical  ad- 
justment are  capable  of  wide  lateral  adjustment,  making  it  possi- 
ble to  reach  any  part  of  large  heavy  work  without  moving  it. 

In  Fig.  541  is  shown  a  two  spindle  gang  manufacturers'  drill 
of  entirely  new  design  and  construction.  This  tool  is  adapted 


FIG.  540. 

to  the  requirements  of  the  manufacturing  plant  having  many 
similar  pieces  to  be  drilled.  In  its  action  the  operator  throws  in 
the  feed  lever  and  the  spindle  instantly  advances  by  a  quick 
movement  until  the  drill  comes  in  contact  with  the  work  surface, 
when  the  regular  feed  starts.  When  the  hole  is  finished  .the 
spindle  automatically  returns.  It  is  therefore  only  necessary  for 
the  operator  to  put  into  and  remove  the  work  from  the  carrying 

Jig- 
In  Fig.  542  is  shown  a  portable  drill  operated  by  a  compressed 
air  motor  through  the  flexible  shaft.     An  electric  motor  or  a  rope 
transmission  may  be  substituted   for  the  compressed  air  motor 


436 


MODERN    MACHINE    SHOP    TOOLS. 


when    desired.     In    many   cases    a    small    air    motor    is    attached 
directly  to  the  drill  spindle. 

When  a  drilling  spindle  is  to  be  used  for  tapping,  it  is  neces- 
sary that  some  provision  be  made  for  reversing  the  spindle.    The 


FIG.  541. 


FIG.  542. 


FIG.  543. 


DRILL  INC.    MACHINES    AND    DRILLING    WORK. 


407 


common  method  is  by  using  a  double  clutch  counter  shaft  with 
one  open  and  one  crossed  driving  belt.  This  arrangement  causes 
a  reversal  of  all  turning  parts  which  is  open  to  some  objection. 
Some  builders  are  employing  a  geared  reversal,  either  directly 
on  the  spindle  or  on  the  first  reducing  shaft.  In  Fig.  543  is 
shown  a  combination  of  three  bevel  gears  for  this  purpose.  Gear 
C  is  keyed  on  the  first  reducing  shaft,  gears  A  and  B  run  loose 
on  the  spindle,  the  clutch  D  is  keyed  to  the  shaft,  but  free  to 


FIG.  544- 

slide  up  or  down  over  the  key.  A  suitable  lever  engages  with  the 
clutch,  thus  making  it  possible  to  lock  gears  B  or  A  with  D,  caus- 
ing the  spindle  to  rotate  forward  or  back,  depending  on  which 
gear  is  made  to  drive.  This  makes  a  very  smooth  and  satisfac- 
tory working  drive. 

It  is  frequently  necessary  to  use  small  drills  in  a  large  machine. 
As  the  spindle  speeds  are  entirely  too  slow  for  the  proper  running 
of  these  drills,  the  high  speed  drilling  attachment  Fig.  544  can 


408  MODERN     MACHINE    SHOP    TOOLS. 

be  used  to  very  good  advantage.  The  box  contains  four  gears,, 
one  cut  on  the  lower  end  of  the  taper  spindle,  another  on  the 
spindle  carrying  the  drill  chuck  with  the  two  others  mounted 
together  on  the  stud  shown.  The  arrangement  is  precisely  like  a 
back  gear  with  an  increasing  rather  than  a  decreasing  spindle 
speed. 

The  securing  of  work  on  the  table  of  the  drilling  machine  re- 
quires clamps,  bolts,  jacks  and  blocking,  the  same  as  for  planer 
and  milling  machine  work.  The  same  care  should  also  be  exer- 
cised in  the  setting,  as  true  work  requires  careful  setting.  The 
use  of  the  square  and  surface  gauge,  and  good  parallel  bars 
are  indispensable  in  setting  up  work  for  drilling.  For  through 
drilling  the  work  must  be  so  located  on  the  table  that  the  drill 
in  passing  through  will  enter  a  slot  or  the  central  hole  on  the 
table.  If  the  drill  is  too  large  or  for  any  other  reason  this  can- 


FIC.  545. 

not  be  done,  the  work  should  be  placed  on  parallel  bars  sufficiently 
thick  to  raise  the  work  enough  to  allow  the  drill  to  pass  through 
without  spotting  into  the  table. 

The  work  table  should  be  kept  in  good  condition,  and  to  drill 
a  hole  into  it  should  be  an  unpardonable  offense.  As  the  work 
table  on  upright  drills  turns  about  its  center  and  the  table  arm 
turns  on  the  column,  it  is  possible  to  so  adjust  the  table  that  any 
point  on  a  piece  of  work  clamped  to  it  can  be  brought  under  the 
center  of  the  drill. 

For  drilling  surfaces  at  right  angles  to  a  plain  surface,  the 
work  can  be  secured  to  a  knee  plate  or  preferably  to  the  table  of 
a  horizontal  spindle  drill.  Round  work  can  be  advantageously 
clamped  in  a  pair  of  90  degree  V  blocks. 

For  the  holding  of  small  and  medium  sized  pieces  of  work 
the  drilling  vise  is  much  used.  In  Fig.  545  is  shown  a  form  of 


DRILLING    MACHINES    AND    DRILLING    WORK. 


40^ 


drilling-  vise  with  an  angular  adjustment  to  the  sliding  jaw  for 
holding  tapered  work.  Nearly  all  pieces  of  work  can  be  held  in 
some  manner  in  a  vise,  and  in  some  cases  when  a  large  number 


FIG.  546A. 


FIG.  5466. 

of  irregular  shaped  pieces  are  to  be  drilled  it  is  found  advisable 
to  make  special  false  vise  jaws  for  holding  them. 

In  Fig.  546  is  shown,  at  A,  a  new  drilling  vise  with  a  cross 
section  at  B.  The  method  of  operating  the  sliding  jaw  in  this 
vise  is  such  as  to  always  hold  the  jaw  tight  down  to  its  slidey 


FIG.  547. 

which  prevents  lifting  and  drawing  the  work  out  of  true  in  tight- 
ening. 

In  Fig.  547  is  shown  a  special  jig  drilling  vise.  It  consists 
of  a  substantially  made  plain  drilling  vise  with  the  jig  drilling 
attachment  shown.  The  attachment  is  secured  to  the  stationary 


410 


MODERN    MACHINE    SHOP    TOOLS. 


jaw.  The  post  C  permits  a  vertical  and  a  turning  adjustment,  and 
is  firmly  clamped  in  position.  The  yoke  D,  which  carries  the 
drilling  bushing  B,  can  be  adjusted  for  length.  The  stops,  H  and 
K,  are  also  adjustable.-  When  a  number  of  pieces  are  to  be  drilled 
alike,  the  first  one  is  clamped  in  the  vise  and  the  stop  K  or  H 
adjusted  to  it.  The  work  should  rest,  if  possible,  on  the  ways  of 
the  vise  or  on  suitable  parallels  in  order  that  all  pieces  can  be 
put  into  the  vise  in  the  same  relative  position.  The  bushing,  when 
properly  adjusted,  insures  the  drilling  cf  the  hole  in  the  same 
relative  position,  within  reasonable  limits,  on  all  the  pieces.  A 
vise  of  this  description  proves  an  efficient  tool  for  many  drilling 
operations. 

No  class  of  work  in  the  manufacturing  shop  presents  as  many 


; 


B 


,\\ 


FIG.  548. 


FIG.  549. 


possibilities  for  jigging  as  does  the  work  handled  in  the  drilling 
machine.  Drilling  is  really  a  connecting  operation  between  the 
machining  and  assembling  of  machine  parts.  These  parts  are 
turned,  planed  and  milled  to  dimensions,  but  the  accuracy  with 
which  they  go  together,  and  their  interchangeability  is  dependent 
entirely  upon  the  manner  in  which  the  drilling  is  performed. 
Carefully  made  drilling  jigs  not  only  make  possible. exact  dupli- 
cation, but  save  much  time  that  would  otherwise  be  devoted  to 
the  laying  out  of  the  wcrk.  Jigs  are  manufacturing  tools  of,  as 
a  rule,  high  first  cost  and  their  economy  depends  very  largely  on 
the  number  of  pieces  to  be  drilled. 

Drilling  jigs  can  be  divided  into  two  general  classes,  plate 
ji^s  and  box  ji^s.  A  plate-drilling  jig  is  one  which  can  be  laid 
flat  upon  the  surface  of  the  work,  properly  located  and  clamped 


DRILLING    MACHINES    AND   DRILLING    \YORK.  4! I 

in  position.  All  holes  drilled  through  plate  jigs  are  parallel  with 
each  other.  A  box  jig  is  one  which  contains  the  work  and  may 
be  used  for  drilling  holes  at  any  angle  with  each  other.  The 
character  of  the  work  frequently  necessitates  the  use  of  a  box 
jig  in  cases  where  all  holes  required  are  parallel  with  each  other.. 
Jigs  are  usually  made  of  cast  iron  with  bushings  of  hardened] 
steel.  The  form  of  bushing  usually  used  is  shown  in  Fig.  548. 
At  A  is  shown  a  shoulder  bushing  for  use  in  jigs  to  be  used  from 
the  one  side  only.  At  B  is  shown  a  plain  bushing,  as  used  in 
plate  jigs  which  are  reversed  for  drilling  from  either  side.  When 
two  bushings,  as  a  drilling  and  a  reaming  bush,  must  be  used  in  the 
same  hole  in  a  jig  they  are  usually  made  as  shown  in  Fig.  549. 
The  knurled  head  facilitates  removing,  and  the  pin  A  prevents 
the  bush  from  turning  and  wearing  loose  in  the  jig.  Bushings 


FIG.  550. 

should  be  nicely  fitted  in  the  plate  and  for  the  most  exacting  re- 
quirements should  be  ground  internally  and  externally  after 
hardening. 

An  example  of  a  plane  plate  jig  is  shown  in  Fig.  550.  This 
jig  is  used  in  the  drilling  of  the  cylinder  head  shown.  The  jig 
is  centered  by  a  short  bush,  'which  fits  the  central  reamed  hole  in 
the  head.  As  the  character  of  the  head  casting  necessitates  the 
jig  being  put  on  in  a  certain  position,  with  reference  to  a  core, 
a  zero  line  established  on  each  casting  and  the  zero  mark  on  the 
ear  shown  on  the  jig,  are  in  each  case  made  to  coincide. 

In  Fig.  551  is  shown  a  reversing  plate  jig  and  the  work  it  is 
used  upon.  In  this  example  the  holes  in  the  bed  are  drilled  and 
those  in  the  cylinder  drilled  and  tapped  to  receive  turned  bolts 
which  fit  the  holes  exactly.  It  is  also  necessary  that  the  flat  face, 
shown  on  the  side  of  the  cylinder,  comes  exactly  at  right  angles 


412  MODERN    MACHINE    SHOP    TOOLS. 

with  the  planed  bottom  of  the  bed.  The  jig  is  first  slipped  over 
the  extended  barrel  of  the  cylinder  and  its  flat  side  squared  with 
the  face  above  referred  to  on  the  cylinder.  The  jig  is  clamped  in 
this  position  and  the  holes  drilled  tapping  size.  The  jig  is  then 
removed  and  the  holes  tapped  at  the  same  setting. 

The  tap  drill  bushings  are  next  removed  from  the  jig  and 


FIG.  551. 

the  bolt  size  bushing  put  in  from  the  opposite  side.  The  ring 
shown  in  the  cut  is  now  slipped  into  the  bore  of  the  bed  and  left 
extending  from  the  face  a  distance  sufficient  to  receive  and  center 
the  jig,  which  is  squared  as  before,  this  time  from  the  drilling  ma- 
chine table.  In  all  cases,  after  drilling  the  first  hole,  the  stop  pin 


FIG.  552. 

shown  should  be  inserted  in  it  to  prevent  any  possibility  of  the 
jig  shifting  on  the  work. 

In  Fig.  552  is  shown  a  form  of  box  jig,  and  the  piece  of  work 
it  is  used  upon.  In  this  case  all  the  holes  are  parallel  with  each 
other  and  three  of  them  do  not  pass  through.  The  work  is  first 


DRILLING    MACHINES    AND    DRILLING    \\ORK. 


413 


faced  and  bored.  All  holes  in  the  jig  are  located  with  reference 
to  the  bore  of  the  work.  The  lower  portion  of  the  jig  holds  the 
work  central  and  the  upper  portion  carries  the  bushings.  These 
parts  are  nicely  fitted  together  and  suitable  dowels  insure  their 
always  remaining  in  the  required  position,  relative  to  each  other. 
For  the  holes  that  are  low  on  the  work  surface,  extended  bush- 
ings are  used. 

In  Fig.  553  is  shown  a  simple  form  of  box  jig  used  for  drill- 
ing holes  in  round  work  at  right  angles  to  each  other.  The 
construction  is  evident  from  the  cut.  The  work  is  slid  to  a  stop 


in  the  jig  and  clamped  in  position.  The  hole  E  is  drilled 
through  the  bushing  C,  and  F  is  drilled  through  the  bushing  D 
with  the  jig  resting  on  its  faces  A  and  B  respectively.  When 
the  angle  A  O  B  is  a  right  angle,  the  holes  will  be  drilled  at  right 
angles  with  each  other.  By  making  the  angle  A  O  B  any  re- 
quired angle  the  same  angular  relation  between  the  holes  drilled 
will  result. 

From  a  consideration  of  Fig.  552  it  is  evident  that  when  holes 
are  to  be  drilled  in  a  piece  of  work  at  any  angle  with  each  other, 
a  box  jig  can  be  used.  This  jig  must  contain  the  work  and  have 
two  parallel  faces,  one  to  receive  the  bush  and  the  other  to  rest 
upon  the  work  table,  at  right  angles  to  each  required  hole. 

The  drilling  of  steel  and  wrought  iron   requires  lubrication 


414 


MODERN    MACHINE    SHOP    TOOLS. 


for  the  cutting  tool.  Cast  iron  and  brass  are  drilled  dry.  As 
with  other  cutting  tools  lard  oil  makes  the  most  satisfactory  lub- 
ricant. It  is  expensive,  however,  and  as  a  result  cheaper  oils 
and  drilling  compounds  comprise  the  lubricants  most  used.  As  the 
lubricant  conducts  away  the  heat  of  friction  generated  in  the  cut- 
ting of  stock,  it  should  be  freely  applied  and  provisions  made  for 
delivering  it  to  the  very  cutting  edge.  This,  as  previously  de- 
scribed, is  accomplished  by  means  of  oil  tube  drills.  These  when 
used  in  a  revolving  spindle  require  a  special  form  of  socket  which 
can  be  connected  by  pipe  or  tubing  with  a  pump,  for  forcing  the 
lubricant. 

The  drilling  of  deep  holes  is  usually  accomplished  in  special 
drilling   machines   using   pod   drills.     Long   twist    drills   are   not 


FIG.  554. 

well  suited  to  the  drilling  of  deep  holes  inasmuch  as  the  strain 
tends  to  untwist  and  make  them  vibrate  and  catch  in  the  work. 
There  is  also  not  sufficient  land  area  to  satisfactorily  guide  the 
drill,  thus  making  it  difficult  to  drill  true,  straight  deep  holes. 
The  pod  drill  is  shown  in  Fig.  554.  It  is  of  semi-circular  cross 
section,  the  radius  of  the  section  being  equal  to  the  radius 
of  the  required  hole.  All  the  cutting  is  done  by  the 
end  face  at  A  B  which  is  given  the  necessary  clearance,  and 
for  drilling  steel  a  small  amount  of  top  rake.  An  oil  tube  D, 
bedded  in  the  shank,  supplies  the  lubricant  to  the  cutting  edge. 
For  this  class  of  drilling  it  is  usual  to  rotate  the  work  to  a  sta- 
tionary drill.  The  feed,  however,  is  usually  given  the  drill.  For 
the  drilling  of  deep  holes  of  large  diameter,  the  drills  used  have 
an  inserted  cutter  which  can  be  removed  for  grinding  and  set 
out  to  compensate  for  wear. 


DRILLING    MACHINES    AND    DRILLING    WORK. 


415 


Spotting  and  facing  of  small  surfaces  is  usually  accomplished 
with  a  counter  boring  tool  of  the  class  shown  in  Fig.  555.  In 
this  tool  the  cutter  is  held  in  place  by  the  small  screw  in  the  end 
of  the  teat.  The  teat  bushings  are  removable,  several  sizes  being 
furnished  with  each  counter  bore.  For  special  work  it  is  advis- 
able to  have  a  separate  counter  bore  for  each  piece.  They  should 
be  made  of  tool  steel  and  the  teat  or  pilot  point  hardened  after  the 


FIG.  555. 

tool  is  finished.  A  plain  mortise  through  the  stock  with  a  small 
set  screw  in  the  center  of  the  teat  is  a  satisfactory  method  of 
holding  the  cutting  blade.  By  reversing  the  blade  this  tool  is 
also  well  suited  for  back  facing  operations. 

In  Fig.  556  is  shown  the  usual  method  of  doing  this  work. 
The  character  of  the  work  is  such  that  the  face  F  cannot  be  ma- 
chined from  the  inside.  The  counter  bore  B  should  be  made  to 
fit  nicely  in  the  hole  and  it  is  also  advisable  to  mill  away  some  of 


FIG.  550. 

the  stock  D  D  on  the  side  of  the  cutter,  in  order  to  give  a  clean 
cutting  edge  close  down  to  the  bar.  A  set  screw  S,  or  some 
other  means  must  be  provided  for  preventing  the  bar  from  draw- 
ing out  of  the  socket. 

When  large  holes  are  to  be  drilled  in  plates,  the  twist  drill 
is  not  well  adapted,  since  its  point  strikes  through  before  the 
land  enters  the  full  size  hole,  thus  leaving  nothing  to  support 
the  cutting  edges.  It  is  also  necessary  for  the  drill  to  reduce  to 
chips  all  the  stock  removed.  For  this  work  the  annular  or  sweep 


416 


MODERN    MACHINE    SHOP    TOOLS. 


drill  is  well  adapted.  Such  a  tool  is  shown  in  Fig.  557.  The 
head  H  carries  two  cutters  C  C  and  the  pilot  P.  The  small  hole 
for  the  pilot  is  first  drilled,  after  which  the  tool  shown  sweeps 
out  the  balance  of  the  stock  with  the  least  possible  amount  of 
cutting  duty. 

When  a  large  hole  of  considerable  length  is  to  be  drilled  it 
is  good  practice  to  drill  a  small  lead  hole  the  required  depth  first. 
This  not  only  aids  in  starting  the  large  drill  true,  but  prevents 
the  grinding  action  on  the  inefficient  cutting  edge,  at  the  end  of 
the  web.  In  cases  of  this  kind  and  for  the  enlarging  of  cored 
holes,  the  three-flute  drill  is  superior  to  the  ordinary  form. 

For  the  handling  of  work  on  the  table  of  the  gang  drill  where 
it  is  necessary  to  move  the  work  from  spindle  to  spindle,  some 


FIG.  557- 


form  of  universal  vise  or  chuck,  that  will  permit  the  work  to  read- 
ily center,  must  be  employed.  If  the  operations  require  but  little 
power  and  consequently  cause  only  a  slight  turning  effort,  the 
work  can  be  held  in  a  drilling  vise  and  moved  to  the  spindles, 
the  operator  centering  and  holding  it  while  the  work  is  done. 
On  heavier  work,  however,  and  in  cases  where  all  spindles  are 
operating  at  the  same  time  a  special  arrangement  must  be  em- 
ployed. 

Take  for  example  the  finishing  of  the  collar  shown  in  Fig. 
558,  which  is  regularly  a  turret  lathe  job.  The  guide  shown 
in  Fig.  559  is  the  same  length  as,  and  secured  to  the  table  in  such 
a  position  that  the  center  line  A  B  is  in  the  plane  of  the  spindles. 
The  chuck  or  vise  for  holding  the  work  is  fastened  to,  or  made 


DRILLING    MACHINES    AND    DRILLING    WORK. 


417 


a  part  of  the  slide,  shown  in  Fig.  560.  This  slide  fits  over  the 
guide,  Fig.  559.  The  work  is  secured  to  the  upper  half  of  the 
slide  which  due  to  the  two  motions  readily  centers  itself  undei 


FIG.  558. 

the  spindle.  After  the  first  spindle  has  performed  its  operation  the 
slide  is  moved  along  the  guide  to  the  next  spindle  and  another 
slide  with  another  piece  of  work  is  put  on  the  guide  and  brought 


FIG.  559. 


to  the  first  spindle.  After  each  operation  the  work  is  moved  to 
the  next  spindle  and  when  finished  the  slide  is  taken  off  the  end 
of  the  guide,  and  returned  to  the  starting  end  for  another  piece. 


MODERN    MACHINE    SHOP    TOOLS. 


.a \. 

I        I 


I       I 

11 


FIG.  560. 


DRILLING    MACHINES    AND   DRILLING    WORK. 


419 


In  this   manner  several   spindles   are  kept  busy,   each   doing  its 
particular  work. 

In  the  present  example,  Fig.  558,  the  chuck  used  can  be  made 
as  shown  in  Fig.  561.  The  ring  R  is  secured  to  the  top  of  the  slider 
and  the  work  W  gripped  by  the  three  set  screws  S  S  S.  In. 
removing  the  work,  but  one  of  these  screws  is  loosened.  The 
work  is  put  in  with  the  top  face  F  down.  The  first  spindle  car- 


FIG.  562. 


FIG.  563. 


ries  a  three-fluted  drill  1-64  inch  under  the  finished  diameter  of7 
the  hole.  The  second  spindle  carries  a  reamer  which  sizes  and: 
finishes  the  hole.  The  third  spindle  carries  the  facing  headi 
shown  in  Fig.  562,  which  consists  of  a  cast  iron  head  H  with  the? 
hardened  and  ground  pilot  pin  P  and  the  inserted  cutter  with  a. 
cutting  edge  at  C  which  sweeps  the  face  E  of  the  work,  leaving^ 
it  smooth  and  true.  By  grinding  the  cutting  edge  perfectly  par- 


42O  MODERN    MACHINE    SHOP    TOOLS. 

allel  to  the  opposite  edge  of  the  cutter  and  securing  it  squarely 
against  the  seat  S  in  the  head  this  tool  will  face  square.  The 
work  is  now  removed  from  the  chuck,  the  upper  half  of  the  slide 
taken  off,  and  the  fixture  X  shown  in  Fig.  563  put  on.  P  is  a  hard- 
ened pilot,  the  upper  end  of  which  is  made  into  an  expanding 
chuck,  as  shown.  The  frame  Y  Y  has  a  bearing  fit  at  S  S  on  the 
pilot  post  and  is  threaded  on  the  nose  of  the  spindle.  A  turning 
tool  T  and  a  facing  cutter  C  are  secured  in  the  proper  positions 
in  the  frame.  The  work  is  secured  to  the  post  as  shown  with 
the  unfinished  face  F  up.  The  downward  feed  of  the  spindle 
first  turns  and  then  faces  the  work. 

The  above  example,  although  involving  simple  operations 
on  a  very  plain  piece  of  work,  serves  to  illustrate  how  many  pieces 
of  work  can  be  put  on  a  gang  drill  and  produced  at  a  much  lower 
cost  than  is  possible  on  a  single  spindle  turret  machine. 

Small  pulleys,  cones  and  plain  work  up  to  6  and  8  inches  iu 
diameter  can  be  advantageously  bored  and  turned  by  the  above 
method  in  the  drilling  machine,  when  they  can  be  gripped  suffici- 
ently rigid  by  the  bore.  When  that  cannot  be  done  the  arrange- 
ment shown  in  Fig.  372  can  be  applied  and  the  work  rotated  to  a 
stationary  cutter. 

The  boring  and  reaming  of  large  parallel  holes  in  the  drilling 
machine  is  accomplished  in  a  very  satisfactory  manner  by  the 
method  shown  in  Fig.  564.  In  this  case  a  5^4 -inch  cylinder  14 
inches  long  is  accurately  bored  in  the  heavy  standard  pattern 
32-inch  upright  drill,  shown  in  Fig.  532.  As  the  bottom  of  the 
engine  bed  shown  is  closed  an  extended  boring  bar  cannot  be  used. 
The  work  is  squared  up  on  the  machine  table  T  and  firmly  clamp- 
ed ;  an  arm  A  supporting  the  upper  end  of  the  work.  The  yoke  Y  is 
bolted  to  the  table  and  extends  into  the  work  through  an  opening 
in  the  side.  This  yoke  carries  a  pilot  bar  P  which  fits  in  a  tap- 
ered bearing  at  E.  The  boring  bar  B  threads  on  the  nose  of  the 
spindle  and  has  a  reamed  hole  H  through  it  to  receive  the  pilot 
bar  P.  The  cutters  C  C  are  secured  in  the  end  of  the  bar  and 
rough  out  the  stock  at  the  first  passage  through  the  bore.  Sizing 
cutters  are  next  substituted  for  C  C  and  the  bore  brought  to 
reaming  size.  At  the  end  of  this  cut  the  facing  cutter  F  which 
is  secured  in  the  head  of  the  bar,  as  shown,  is  carried  down  and 
the  end  of  the  cylinder  faced  by  a  sweep  cut. 

The  construction  of  the  end  of  the  bar  is  such  that  the  cut- 
ters C  C  and  the  sizing  cutters  can  be  changed  without  altering 


DRILLING    MACHINES    AND    DRILLING    WORK. 


421 


their  dimensions.  This  is  especially  important  with  the  sizing 
cutter,  as  it  will  carry  through  several  bores  without  regrinciing. 
The  pilot  bar  P  is  now  taken  out  and  an  inserted  blade  reamer 


FIG.  564. 

secured  on  the  end  of  the  boring  bar  is  floated  through  the  bore 
leaving  .it  smooth,  round  and  parallel. 

The  reamer  used  on  the  above  work  comes  from  the  shop  of 


422 


MODERN    MACHINE    SHOP    TOOLS. 


the  B.  F.  Barnes  Company,  and  its  size  retaining  features  are  of 
special  interest. 

It  is  shown  in  Fig.  565.  The  cutters,  one  of  which  is  shown 
at  A  and  B,  are  inserted  in  the  head,  as  shown.  The  shank  of 
each  cutter  is  tapered  and  drawn  firmly  to  its  seat  by  the  bolt 
shown  in  B.  The  cutter  disc  corresponds  to  one  thread  of  a 
coarse  pitch  square  thread  screw,  a  portion  of  which  is  ground 
away,  as  shown  at  C.  In  obtaining  the  required  size,  the  cut- 
ters are  numbered,  hardened  and  fitted  in  the  head.  The  head 
is  then  placed  on  a  mandrel  between  centers  in  the  grinding  ma- 
chine and  the  cutters  ground  to  the  circle  D  D  of  the  exact  di- 
ameter required.  They  are  then  removed  and  each  cutter  ground 


FIG.  565. 

to  the  diameter  E  E,  and  replaced  in  the  head,  each  cutter  in  its 
respective  bearing  as  indicated  by  the  numbers.  This  is  im- 
portant inasmuch  as  the  locations  of  the  bearings  vary  somewhat 
and  consequently  all  the  cutters  are  not  of  the  same  diameter. 

The  cutting  edge  can  be  set  to  a  line  across  the  face  of  the 
liead  and  by  grinding  from  the  face  X  only  in  sharpening,  the 
•exact  diameter  of  the  tool  can  be  maintained  until  the  cutters 
are  entirely  ground  away.  By  keeping  a  record  of  the  diameter 
-of  each  cutter,  others  can  be  made  at  any  time  without  the  ne- 
cessity of  the  first  grinding  operation  above  referred  to.  The 
•objection  to  this  tool  is  its  comparatively  short  cutting  edges. 
It  is  only  adapted  to  reamers  of  the  larger  sizes,  as  enough  cutters 
cannot  be  put  in  a  head  of  small  diameter. 


CHAPTER    XXVIII. 

GRINDING    MACHINES   AND   GRINDING. 

Grinding  operations  in  the  machine  shop  depend  upon  the 
abrasive  or  cutting  qualities  of  stone,  emery,  corundum,  and  car- 
borundum, when  suitably  held  and  presented  to  the  work.  The 
use  of  the  solid  grinding  wheel  has  made  it  possible  to  attain 
many  refinements  in  machine  construction  that  would  have  been 


FIG.  566. 

impossible  without  it.  It  has  made  it  practical  to  economically 
finish  parts  in  hardened  steel  that  could  not  possibly  be  machined 
with  cutting  tools  in  the  lathe  or  planer;  and  on  the  softer 
materials,  surfaces  smoother  and  truer  can  be  obtained  by  grind- 
ing than  by  any  other  method. 

Grinding  operations  may  be  divided  into  the  following  classi- 


424  MODERN    MACHINE    SHOP    TOOLS. 

fications :  ist,  hand  grinding;  2d,  tool  and  cutter  grinding;  3d, 
cylindrical  grinding;  4th,  surface  grinding.  Hand  grinding  in- 
cludes all  the  grinding  operations  in  which  the  work  is  held  to  the 
wheel  by  hand  or  with  a  rest,  as  in  rough  grinding,  ordinary 
lathe  tool  grinding,  buffing  and  polishing.  The  class  of  machine 
used  for  this  work  is  of  the  simplest  form,  .consisting  of  the 
wheel-carrying  spindle  mounted  in  suitable  bearings  on  a  sub- 
stantial head  or  pedestal.  In  Fig.  566  is  shown  a  simple  grind- 


FIG.  567. 

ing  stand,  designed  to  carry  two  wheels.  It  is  provided  with  ad- 
justable rests  upon  which  the  work  being  ground  is  steadied. 
This  grinder  is  intended  for  dry  grinding  of  the  rough  and  heavy 
class,  where  there  is  little  danger  of  heating  the  work. 

When  tempered  work  is  to  be  ground,  or  any  class  of  work 
that  would  be  injured  by  heating,  a  wet  grinder  of  the  class  shown 
in  Fig.  567  is  used.  With  tools  of  this  class  a  supply  of  water  is 
delivered  constantly  to  the  rim  of  the  wheel,  thus  keeping  the 


GRIXDI.XC    M.UHIXKS    AXU    GRIXDING.  425 

work  cool.  Fig.  568  shows  a  buffing  head  or  spindle.  The 
spindle  extends  well  out  from  its  bearings  for  convenience  in 
handling  the  work  being  operated  upon.  These  spindles  are 
fitted  to  receive  wheels  of  wood,  leather,  or  cloth,  which  are 
charged  with  the  emery  or  other  grinding  material.  The  work 
is  held  to  the  wheel  without  the  aid  of  a  rest. 

Tool  and  cutter  grinding  requires  a  better  class  of  grinding 
machinery  than  is  required  for  the  hand-grinding  operations. 
What  is  here  referred  to  as  tools  does  not  include  the  ordinary 
hand  and  lathe  tools,  commonly  ground  on  the  machine  shown  in 
Fig.  567,  but  refers  to  drills,  reamers,  milling  cutters,  and  the 
finest  class  of  tools.  Fig.  569  illustrates  a  universal  cutter  and 


FIG.  568. 

reamer  grinder.  As  the  name  implies  these  tools  are  provided 
writh  all  the  necessary  adjustments  and  attachments  for  grinding 
the  cutting  edges  of  all  classes  of  reamers  and  milling  cutters, 
and  in  many  cases  may  be  used  for  doing  a  limited  amount  of 
cylindrical  grinding  both  internal  and  external.  A  much  simpler 
machine,  shown  in  Fig.  570,  constitutes  a  very  satisfactory  cutter 
grinder  of  small  proportions.  By  the  use  of  the  swivel  head 
shown,  cutters  of  all  angles  may  be  readily  ground,  and  by  plac- 
ing centers  on  the  slide  which  is  operated  by  the  lever  shown 
under  the  table,  reamers  up  to  the  capacity  of  the  machine  may 
be  ground. 

The  extensive  use  of  the  rotating  cutter  in  machining  opera- 
tions and  the  necessity  of  keeping  these  cutters  true  and  sharp 
makes  necessary  the  use  of  the  cutter  grinder  whenever  this  class 


MODERN     MACHINE    SHOP    TOOLS. 


FIG.  560. 


GRINDING    MACHINES    AND   GRINDING. 


427 


-of  tools  are  used.  In  the  grinding  of  cutters  care  and  judgment 
must  be  exercised  and  not  until  the  operator  has  become  thor- 
oughly familiar  with  all  the  setting  combinations  of  the  machine 
can  he  expect  to  get  the  best  results. 

As  water  is  not  used  on  the-  wheels  of  cutter  grinders  and 
the  wheels  are  for  this  work  usually  quite  hard  and  fine,  light  cuts 


FIG.  570. 


FIG.  571. 

must  be  taken  in  order  not  to  draw  the  temper  of  the  tool  at  its 
cutting  edge.  The  cutter  support  should  be  adjusted  to  bear 
against  the  tooth  being  sharpened  and  its  position  relative  to  the 
wheel  should  be  such  as  to  give  the  necessary  amount  of  clear- 
ance to  the  cutting  edge. 

Polishing  and  buffing  operations   involve  the   removal  by  a 
grinding  process  of  a  small  part  of  the  work  surface,  the  grind* 


428  MODERN    MACHINE    SHOP    TOOLS. 

ing  material  used  being  of  such  a  fine  character  as  to  leave 
a  smooth,  highly-finished  surface.  This  class  of  work  is  usual!}7 
done  on  the  buffing  spindle  shown  in  Fig.  568.  Buffing  does 
not  leave  a  true  surface  and  is  consequently  confined  strictly  to 
polishing  work. 

The  grinding  of  twist  drills  is  a  very  particular  operation, 
requiring  a  skillful  operator,  if  performed  by  hand.  In  Fig.  571 
is  shown  a  twist-drill  grinder  in  which  the  twist  drills  may  be 
ground  with  the  assurance  that  the  angle  and  clearance  will  be 
correct  and  equal  on  both  sides. 

In  the  machine  shown,  the  construction  is  such  that  drills  of 
any  diameter  within  the  limits  of  the  machine  may  be  ground 
with  but  one  preliminary  adjustment  for  each  size. 

Unfortunately  a  twist  drill  can  be  ground  by  hand  on  a  plain 
emery  wheel,  which  fact  keeps  the  twist  drill  grinder  out  of  many 
shops  where  its  use  would  add  materially  to  the  efficiency  of  the 
drilling  equipment.  Correctly  ground  drills  cut  faster,  stand  up 
longer  between  grindings  and  produce  the  proper  size  of  hole. 
A  correctly-ground  drill  seldom  breaks,  as  it  cuts  freely  ahead  of 
its  feed  and  does  not  scrape  and  jam,  as  is  the  case  when  clear- 
ance and  angle  are  wrong. . 

Grinding  machines  for  the  grinding  of  common  forged  lathe 
and  planer  tools  are  manufactured,  and  in  shops  where  large 
numbers  of  forged  tools  are  used  have  proved  very  efficient.  In 
the  working  of  these  grinders  the  tool  is  clamped  in  a  suitable 
head  and  presented  to  the  emery  wheel  at  the  proper  rake  and 
clearance  angles. 

Cylindrical  grinding  as  a  class,  covers  all  forms  of  grinding 
operations  upon  external  and  internal  cylindrical  surfaces.  The 
universal  grinding  machine,  or,  as  it  is  sometimes  termed,  grind- 
ing lathe,  shown  in  Fig.  572,  is  specially  adapted  to  this  very  ex- 
acting class  of  work.  All  machines  of  this  class  consist  of  a 
swivel  table  carrying  a  suitable  head  and  tail  stock,  and  of  a 
wheel  stand  carrying  the  grinding  wheel.  The  arrangement  of 
parts  is  such  that  either  the  wheel  stand  is  ^iven  the  feeding  mo- 
tion past  a  stationary  table  or  the  platen  is  given  the  feed  past 
the  wheel.  The  adjustments  are  such  that  the  wheel  can  be  set 
in  or  away  from  the  line  of  the  work  center,  or  can  be  turned  to 
stand  at  any  desired  anele  with  the  line  of  the  feed  travel,  which 
is  necessary  for  face  and  steep  angle  grinding.  The  swivel  table 
can  be  set  at  an  an^le  with  its  travel,  or  the  line  of  travel  of  the 


GRINDING    MACHINES    AND    GRINDING.  429 

wheel  where  the  table  is  stationary,  thus  making  possible  the 
grinding  of  long  tapers.  For  internal  grinding,  a  small  spindle, 
run  at  a  high  rate  of  speed  and  carrying  an  emery  wheel  small 
enough  in  diameter  to  operate  in  the  bore  to  be  ground,  is  used. 
These  machines  are  provided  with  suitable  pumps  for  supplying 
an  abundance  of  water  to  the  wheel  and  work,  when  the  character 
of  the  work  is  such  as  to  require  it.  As  these  machines  are  ex- 
pected to  produce  work  smooth  and  cylindrically  true,  they  are 
most  carefully  built,  and  should  embody  all  the  refinements  known 
in  machine  tool  construction.  The  spindle  for  carrying  the  emery 
wheel  is  perfectly  balanced  and  runs  in  very  close-fitting  boxes, 
as  any  slack  in  the  bearings  or  lack  of  balance  proves  fatal  to  the 
production  of  correct  results.  Provisions  are  made  for  rotating 
the  work,  when  held  between  dead  centers,  with  a  spring  tension 
adjustment  on  the  tail  center,  thus  reducing  the  danger  due  to 
expansion  and  the  unequal  wearing  of  the  center  bearings.  The 
screw  adjustment  fcr  setting  the  wheel  up  to  work  is  graduated 
to  thousands  of  an  inch,  thus  forming  an  excellent  guide  in  de- 
termining the  amount  of  stock  removed. 

The  application  of  an  automatic  cross  feed  to  the  wheel  stand 
is  a  valuable  addition  to  the  plain  and  universal  machines,  as  it 
advances  the  wheel  to  the  work  by  fixed  amounts  at  the  begin- 
ning of  each  cut,  thus  making  the  conditions  more  uniform  and. 
requiring  less  attention  on  the  part  of  the  operator.  The  amount 
of  feed  for  each  passage  of  the  wheel  over  the  work  can  be  varied 
to  suit  the  condition.  A  feed  as  fine  as  y%  of  ^TMTO  can  be  OD~ 
tained,  which  would  reduce  the  work  Y\  of  y^nr  ^or  eacn  passage 
of  the  wheel  across  it.  An  automatic  stop  throws  out  the  feed 
when  the  wheel  has  advanced  the  required  amount.  As  this 
mechanism  is  necessarily  very  sensitive  and  delicate  it  must  be 
kept  perfectly  clean  and  wrell  lubricated. 

Plain  grinding  machines  are  in  many  respects  similar  to  the 
universal  machines.  As  they  are,  however,  used  for  straight 
cylindrical  and  long  tapered  work,  many  of  the  universal  features 
are  dispensed  with,  making  them  strictly  a  manufacturers'  ma- 
chine. 

The  wheel  for  any  class  of  grinding  should  be  properly 
adapted  to  its  work  as  to  shape,  grade,  and  hardness.  The  shape 
and  character  of  the  work  determine  in  any  case  the  shape  of  the 
wheel  to  use ;  while  the  material  of  which  the  work  is  composed, 
the  amount  of  metal  to  be  removed,  and  the  condition  of  the 


43O  MODERN    MACHINE    SHOP    TOOLS. 

finished  surfaces  must  determine  the  quality  of  the  wheel.  Emery 
and  other  wheels  of  that  class  are  composed  of  two  elements — 
the  abrasive  and  the  cementing  materials.  The  cement — as  clay, 
glue,  or  rubber — holds  together  the  grains  of  emery,  and  in  use 
as  the  grains  become  worn  and  dulled,  they  break  away  from 
their  settings  in  the  cement,  and  fresh  grains  are  uncovered  to 
go  on  with  the  cutting  process.  If  this  breaking  down  process 
is  comparatively  rapid,  the  wheel  cuts  very  freely,  but  reduces  in 
diameter  correspondingly  fast.  If  the  cement,  on  the  other  hand, 
does  not  give  up  the  worn  grains  of  emery,  the  wheel  glazes,  cuts 
slowly,  and  heats  the  work.  The  surface  velocity  of  the  wheel 
should  be  correct  for  the  different  classes  of  work  and  grade  of 
wheel.  The  wheel  is  ordinarily  most  efficient  just  before  it  stops 
breaking  away  and  begins  to  glaze.  Up  to  this  point,  the  higher 
the  speed  the  more  metal  it  will  remove  in  a  given  length  of 
time.  When  run  at  lower  speed,  it  cuts  somewhat  easier,  and 
does  not  heat  the  work  as  badly.  Glazing  is  usually  prevented 
by  reducing  the  speed.  Soft  wheels  stand  up  better  at  high, 
than  at  low  speeds.  The  wider  the  faces  of  the  wheel  presented 
to  the  work,  the  more  cutting  surface,  and  the  faster  the  metal 
is  ground  away.  The  feeds  must  be  correspondingly  coarse. 
The  wider-faced  wheels  should  be  comparatively  soft,  and  as  the 
face  reduces  in  width  the  wheel  should  increase  in  hardness. 

The  surface  speed  of  the  work  should  be  proportionate  to 
the  speed  of  the  wheel,  and  in  any  case  should  be  sufficiently  slow 
to  allow  the  wheel  ample  time  to  cut  away  the  metal  without 
crowding,  as  otherwise  the  work  is  sprung  away  from  the  wheel 
more  or  less,  and  untrue  work  results. 

A  free  cutting  wheel,  run  at  the  proper  speed  and  with  a  light 
cut,  is  best  for  accurate  grinding,  as  it  removes  the  metal  without 
pressure  and  consequently  cuts  the  high  spots  most  and  does 
not  heat  up  the  work.  It  is,  however,  necessary  on  very  accurate 
work  to  use  water  on  the  wheel,  as  a  slight  change  of  tempera- 
ture affects  the  work  noticeably.  When  long  cuts  are  to  be  taken, 
it  is  sometimes  difficult  to  get  the  wheel  to  stand  up  so  as  to  give 
a  parallel  cut.  In  such  cases,  the  wheel  must  be  properly  adapted, 
and  each  grain  of  emery  must  cut  as  long  as  possible  before  drop- 
ping out.  As  the  harder  wheels  hold  the  emery  longer,  and  can 
be  run  somewhat  slower,  they  are  best  adapted  to  this  condition. 
The  wheel  should  have  a  wide  face,  and  should  be  of  large  diam- 
eter, so  as  to  present  as  many  grains  of  the  abrasive  as  possible 


GRINDING    MACHINES    AND    GRINDING. 


431 


to  perform  the  required  work.  It  is  also  necessary  to  use  the 
coarser  feed  and  light  cuts  in  order  that  the  wheel  may  cover 
the  entire  surface  before  it  drops  materially  in  diameter.  The 
direction  of  feed  is  changed  for  each  time  over  the  work,  which 
also  tends  to  even  up  the  wear  on  the  wheel. 

All  manufacturers  of  grinding  wheels,  however,  give  a  table 
of  speeds  for  the  different  diameter  of  wheels  they  manufacture, 
but  these  speeds  are  not  always  best  suited  to  the  work.  All 
wheels  should  fit  easily,  yet  closely,  on  their  spindle  to  prevent 
danger  from  cracking,  and  a  soft  washer  of  uniform  thickness 
should  be  placed  between  the  sides  of  the  wheel  and  the  clamp- 
ing washer.  The  wheel  should  be  firmly  clamped  and  trued  be- 
fore using.  Manufacturers  test  all  wheels  by  running  them 
at  a  speed  considerably  above  their  rated  speed. 

In  the  grinding  of  long  work  it  is  quite  necessary  to  support 
it  at  one  or  more  points  between  its  end  bearings,  as  otherwise 
it  will  spring  and  chatter,  making  true  smooth  work  impossible. 
For  this  purpose,  suitable  steady  and  follow  rests  are  provided 
with  the  machine. 

In  Fig.  573  is  illustrated  the  method  of  grinding  slight  tapers 


FIG.  573. 


432 


MODERN    MACHINE    SHOP    TOOLS. 


in  the  universal  or  plain  grinding  machines.  By  means  of .  a 
screw  and  graduation  at  the  end  of  the  table  it  is  swiveled  to  the 
required  angle  with  the  line  of  travel  of  the  slide.  In  this  man- 
ner tapers  up  to  il/2  or  2  inches  per  foot  may  be  ground.  When 
a  steeper  taper  is  required  it  can  be  obtained  in  the  universal  ma- 
chine by  setting  the  wheel  slide  to  the  required  angle,  as  shown 
in  Fig.  574.  In  this  particular  case,  two  tapers,  one  of  45  de- 
grees and  one  of  5  degrees  are  required  on  the  work.  By  swing- 


r.oy 


FIG.   574. 

ing  the  swivel  table  to  5  degrees  from  the  line  of  its  trave1  the 
slight  taper  can  be  ground  by  the  travel  of  the  table  past  the  wheel. 
By  setting  the  wheel  slide  to  50  degrees,  as  shown,  the  steep 
taper  is  ground  by  operating  the  wheel  slide,  the  swivel  table  re- 
maining stationary.  If  but  the  45  degree  taper  was  required,  the 
table  would  be  left  central,  and  the  wheel  slide  set  to  45  degrees. 
As  shown  in  the  cut,  the  corner  of  the  wheel  is  dressed  to  give 
a  cutting  face  of  suitable  width. 


GRINDING    MACHINES    AND    GRINDING. 


433 


Tn  Fig-.  575  is  shown  the  usual  method  of  face  grinding.  The 
work  is  held  in  the  chuck  or  on  a  face  plate  as  shown.  If  the 
face  is  to  be  a  plane  surface,  the  head  spindle  axis  is  set  at  right 
angles  to  the  wheel  spindle.  By  varying  this  angle  concave  or 
convex,  conical  surfaces  may  be  obtained. 

In  Fig.  576  is  shown  the  method  of  grinding  internal  surfaces 


FIG.  575. 

with  the  internal  fixture.  The  example  given  serves  to  illustrate, 
as  in  Fig.  574,  the  settings  for  both  slight  and  steep  tapers.  The 
small  taper  is  obtained  by  setting  the  swing  table  to  the  required 
angle  with  the  travel  of  the  table  slide  and  the  steep  taper,  by 
using  the  wheel  slide  set  to  give  the  wheel  the  required  line  of 
travel.  It  will  be  noted  that  in  using  the  internal  grinding  fix- 
ture, the  position  of  the  wheel  table  is  reversed  from  its  universal 


434 


MODERN    MACHINE    SHOP    TOOLS. 


position  and  the  fixture  secured  to  the  end  of  the  table.  A  belt- 
ing jack  is  substituted  for  the  emery  wheel  spindle  and  the  spindle 
of  the  internal  fixture  driven  by  a  light  canvas  belt  from  the  jack. 
Although  the  spindle  of  the  internal  grinding  fixture  is  driven 
at  a  very  high  speed,  the  diameters  of  the  wheels  used  are  so  small 
that  it  is  not  possible  to  obtain  a  periphery  speed  as  high  as  would 


FIG.  576. 


be  desired.     It  therefore  is  necessary  to  use  a  free  cutting  wheel 
and  to  rotate  the  work  to  it  at  a  comparatively  slow  speed. 

On  these  machines  all  work  and  wheel  settings  are  to  care- 
fully graduated  arcs.  These  graduations  cannot,  however,  be 
relied  upon  for  exact  settings  within  the  accuracy  limit  of  the 
machine.  If,  for  example,  the  machine  is  set  for  parallel  grind- 
ing on  a  certain  class  of  work,  the  head  stock  is  undamped  and 
the  spindle  thrown  out  of  parallel  with  the  table's  line  of  travel ; 
it  will  be  found  practically  impossible  to  set  the  head  back  to  its 


GRINDING    MACHINES    AND    GRINDING. 


435 


original  position,  sufficiently  close  to  make  the  machine  grind 
parallel  again.  In  fact,  so  minute  are  the  variations  that  the  wheel 
will  detect  that  the  unclamping  of  the  tail  stock,  moving  it  out  of 
position  and  then  back  will  show  an  unparallel  condition  of  the 
work.  It  therefore  becomes  necessary  after  each  setting  of  head 
or  tail  stock  to  readjust  the  work  table  by  means  of  the  end  ad- 
justing screw  in  order  that  the  line  of  rotation  may  be  brought 
parallel  with  the  line  of  motion  of  the  table  slide. 

Surface  grinding  bears  the  same  relation  to  planing  that  cyl- 


FIG.  577. 


indrical  grinding  does  to  turning.  The  surface  grinders  use  the 
same  form  of  wheels  as  the  cylindrical  grinding  machines.  The 
work,  however,  is  secured  to  the  work  table,  which  is  fed  under 
or  over  the  wheel.  In  Fig.  577  is  shown  a  surface  grinding  ma- 
chine. The  construction  of  the  machine  is  clearly  shown.  The 
wheel  is  adjustable  vertically  to  give  depth  of  cut,  the  arrange- 
ment of  pulleys  being  such  as  to  give  constant  tension  on  the 
belt  for  all  positions  of  the  wheel.  The  cross  feed  is  obtained 
by  moving  the  table  toward  or  away  from  the  housings  on  suit- 


436 


MODERN    MACHINE    SHOP    TOOLS. 


able  cross  slides.     Provisions  are  made  for  supplying  water  to 
the  wheel  when  necessary. 

In  Fig.  578  is  shown  a  plain  grinder  provided  with  a  surface 
grinding  plate.  In  this  case  the  wheel  projects  above  the  surface 
of  the  plate  only  the  amount  of  the  cut  required,  and  the  work  is 
passed  over  it  by  hand.  To  give  satisfactory  results,  the  spindle 
and  its  bearing  should  be  first  class,  and  the  wheel  in  perfect  bal- 
ance. A  grinder  of  this  class  is  a  most  satisfactory  tool  for 


FIG.  578. 

smoothing  and  polishing  surfaces  where  finish  and  not  truth  is 
required.  A  more  refined  grinder,  somewhat  after  the  same 
order,  and  known  as  a  disc  grinder  is  shown  in  Fig.  579.  These 
are  very  nicely  constructed  grinders  in  which  the  grinding  is 
done  by  sheet  emery  glued  to  the  faces  of  the  discs.  The  rests 
swing  across  the  face  of  the  disc,  the  work  being  held  on  top  of 
the  rest.  For  the  finishing  of  one  or  more  plane  surfaces  on 
small  parts,  this  tool  is  very  well  adapted. 


GRINDING    MACHINES    AND    GRINDING. 


437 


In  Fig.  580  is  shown  a  form  of  portable  hand  emery  grinder 
driven  by  a  rope  transmission  through  a  flexible  shaft.  These 
grinders  are  very  satisfactory  tools  for  the  grinding  of  heavy 
castings  that  cannot  be  held  to  a  wheel. 

For  truing  the  emery  wheels  used  on  the  better  classes  of 
grinding  machinery  nothing  but  a  black  diamond  truer  is  suitable. 
Such  a  tool  is  shown  in  Fig.  581.  The  diamond  is  mounted  in 
the  end  of  the  round  steel  holder,  as  shown.  The  round  holder 


FIG.  579. 

enables  the  stone  to  be  presented  to  the  wheel  in  various  posi- 
tions, so  as  to  bring  the  several  cutting  points  of  the  stone  into 
action.  As  the  diamond  is  harder  than  the  emery,  it  actually  cuts 
the  wheel  a\vay. 

A  suitable  fixture  is  usually  provided  for  holding  the  truer 
in  such  a  manner  that  it  can  be  passed  squarely  by  the  part  of  the 
wheel  being  trued.  Water  should  be  used  on  the  wheel  in  true- 
ing  and  the  cuts  should  be  light  in  order  to  obtain  good  results 
and  to  preserve  the  diamond. 

For  the  coarser  \vheels,  dressers  of  the  character  of  the  one 


438 


MODERN    MACHINE    SHOP    TOOLS. 


shown  in  Fig.  582  are  used.  Several  forms  of  discs  are  used.. 
The  discs  are  made  of  hard  steel  or  chilled  iron  and  turn  freely 
upon  a  pin.  In  their  action  the  teeth  of  the  discs  break  up  the 
surface  of  the  wheel  as  they  roll  together  and  dislodge  the  high 
particles  of  the  wheel  by  a  picking  action. 

Lapping  is  a  refined  grinding  process  used  for  the  final  finish- 
ing of  machine  ground  surfaces,  usually  of  hardened  steel.  A 
lap  is  usually  made  of  cast  iron,  copper  or  lead,  the  surface  being 


FIG.  582A. 


FIG.  580. 


FIG.  581. 


FIG.  5826. 


coated  with  very  fine  washed  emery.  In  Fig.  583  is  shown  a 
form  of  lap  well  suited  to  the  finishing  of  cylindrical  surfaces. 
The  body  of  the  lap  is  of  cast  iron  with  lead  or  copper  strips 
a  a  a  a  extending  through  it.  These  soft  strips  serve  to  hold  the 
emery  better  than  a  harder  material.  By  slightly  reducing  the 
diameter  of  the  lap  by  means  of  the  thumb  screw,  as  the  grind- 
ing proceeds,  the  work  may  be  brought  to  the  required  size.  In 
its  use,  the  work  is  usually  rotated  at  a  comparatively  high  speed, 
and  the  lap  held  by  the  hand.  By  moving  it  slowly  from  end  to 
end  of  the  surface  being  finished,  parallel  work  can  be  obtained. 


GRINDING    MACHINES   AND   GRINDING. 


439 


It  is  in  this  manner  that  hardened  steel  plugs  receive  their  final 
sizing. 

For  the  finishing  of  bores  the  same  general  method  is  em- 
ployed. A  plug,  preferably  with  the  lead  or  copper  strips, 
so  constructed  that  it  can  be  slightly  expanded,  is  the  form  usual- 
ly employed.  In  Fig.  584  is  shown  a  form  well  suited  to  most 
classes  of  work.  It  is  preferably  of  cast  iron  but  may  be  made 
of  soft  steel.  The  slot  is  cut  through  and  the  wedges  w  w  serve  to 
give  the  slight  expansion  necessary. 

For  the  lapping  of  flat  surfaces,  a  cast  iron  plate  drilled  full 


FIG.  583. 


FIG.  584. 

of  holes  with  plugs  of  lead  or  copper  inserted  and  the  surface 
then  planed  as  true  as  possible  can  be  used.  This  surface  is 
charged  with  emery  and  oil  and  the  work  rubbed  over  it,  the  di- 
rection of  motion  and  part  of  the  surface  used,  being  constantly 
changed  in  order  to  wear  the  lap  equally  all  over. 

Although  it  is  impossible  to  give  any  fixed  rule  for  the  cor- 
rect periphery  speed  of  emery  wheels  of  different  makes  and  for 
varying  service,  the  tables  given  in  Chapter  XXXIV.  will  serve 
as  suitable  guides. 


CHAPTER   XXIX. 

HARDENING   AND  TEMPERING. 

The  hardening  and  tempering  of  tool  steels  present  many 
problems  which  can  only  be  solved  by  a  wide  and  varied  experi- 
ence at  the  temperer's  forge.  The  simpler  cases  are  mastered 
with  little  trouble,  but  when  it  comes  to  the  tempering  of  difficult 
and  expensive  pieces  the  trained  judgment  of  the  expert  temperer 
is  usually  sought. 

Hardening  and  tempering  of  steel  brings  about  such  a  change 
in  its  physical  condition  that  it  may  be  used  in  places  where  cut- 
ting edges,  resistance  against  wear  and  elasticity  are  required. 

The  hardening  and  tempering  of  steel  are  two  quite  different 
things  although  often  referred  to  as  the  same.  By  hardening 
we  change  the  physical  condition  of  the  steel,  transforming  it 
from  a  relatively  soft  material  to  an  exceedingly  hard  one  and  at 
the  same  time,  rendering  it  brittle  and  weak.  By  tempering  we 
reduce  the  hardness  to  the  degree  required  for  performing  the 
work  it  is  intended  for,  and  in  so  doing  restore  much  of  its  origi- 
nal strength  and  toughness.  For  tempering  it  is  therefore  neces- 
sary that  a  degree  of  hardness  equal  to  or  greater  than  that  re- 
quired must  first  be  given  the  steel. 

The  amount  of  carbon  contained  in  a  piece  of  steel  determines 
its  temper.  The  more  carbon,  the  higher  the  temper.  Thus 
i%  per  cent  of  carbon  makes  a  steel  capable  of  very  high  temp- 
ers, such  as  are  required  for  the  turning  of  chilled  rolls  and  other 
very  hard  materials.  One  per  cent  is  the  amount  usual  when 
the  steel  is  used  for  the  more  common  tools,,  as  cold  chisels, 
drifts,  etc.  Lathe  tools,  milling  cutters,  taps,  drills,  and  reamers 
come  between  these  two  limits.  In  general,  the  more  the  carbon, 
the  greater  the  care  required  in  the  heating  and  handling  of  the 
steel.  A  iy2  per  cent  carbon  steel  burns  very  easily  while  a  one 
per  cent  steel  can  be  heated  with  little  danger  from  this  source. 

Cutting  tools  that  are  forged  to  shape  are  given  a  short 
temper ;  that  is  only  a  short  portion  at  the  cutting  edge  is  made 
hard,  the  balance  of  the  tool  being  left  tough  to  support  the  cut- 
ting edge,  and  when  that  edge  is  worn  or  ground  back  into  the 
softer  part  the  tool  is  redressed  and  retempered.  When,  as  with 


HARDENING    AND   TEMPERING.  44! 

a  drill  or  milling  cutter,-  the  tool  must  be  repeatedly  sharpened 
until  worn  completely  out  without  retempering,  it  is  necessary 
to  harden  it  through  and  then  draw  down  for  toughness  as  far  as 
the  character  of  the  tool  will  permit.  Cutters,  reamers  and 
mandrels  of  comparatively  large  diameter  are  usually  given  a 
hard  surface  temper,  leaving  the  core  soft. 

When  a  piece  of  steel  is  of  sufficiently  high  temper  to  be  used 
as  a  metal  cutting  tool  it  is  too  hard  to  permit  of  any  bending. 
By  drawing  the  temper  sufficiently  low,  however,  the  steel  gains 
in  toughness  at  the  expense  of  its  hardness  and  what  is  termed  a 
spring  temper  is  obtained. 

The  tempering  of  steel  machine  parts  to  make  them  resist 
wear  is  frequently  necessary.  The  higher  the  temper  the  better 
the  wear  reducing  quality ;  the  hardness,  however,  being  limited 
by  the  strength  required. 

The  manufacturers  of  tool  steels  usually  prefer  to  recommend 
the  grade  and  temper  of  steel  for  any  specific  purpose.  In  gen- 
eral, the  higher  the  carbon  the  finer  the  steel,  but  not  necessarily 
the  better  for  many  classes  of  work.  For  general  purposes  a 
grade  of  steel  of  medium  temper  costing  about  twelve  cents  per 
pound,  as  furnished  by  any  of  the  reputable  makers,  will  be 
found  satisfactory.  The  extra  qualities  at  16  to  20  cents  per 
pound  are  suitable  for  the  most  exacting  requirements,  while  a 
lower  grade  at  eight  cents  can  be  used  for  the  less  important  work. 
For  many  machinery  parts,  when  a  temper  to  resist  wear  only  is 
required,  the  lowest  grades  of  tool  steel  or  even  machinery  steel 
can  be  used.  The  latter  is  not  considered  as  a  tempering  steel, 
but  can  be  somewhat  hardened  by  tempering  methods ;  and  can 
be  given  a  hard  surface  by  case  hardening.  There  are  many 
special  grades  of  steel  running  much  higher  in  price;  their  uses 
being  restricted  to  certain  lines. 

The  heating  of  steel  may  be  classed  under  three  distinct  heads ; 
first,  for  forging ;  second,  hardening,  and  third,  for  tempering. 
For  forging,  a  clean,  thick  fire  should  be  used  with  a  steady  blast, 
so  regulated  as  to  give  a  uniform  heat  to  the  work.  It  is  very 
important  that  the  work  be  heated  uniformly  and  at  the  same  time 
it  is  advisable  to  get  this  heat  as  quickly  as  possible,  as  it  usually 
injures  the  quality  of  the  steel  to  leave  it  too  long  in  the  fire. 

If  the  steel  is  not  uniformly  heated,  the  forging  produces  sur- 
face cracks,  makes  the  grain  of  the  steel  coarse  and  is  otherwise 
injurious.  Heavy  forging  at  moderate  heats  refines  and  improves 


442  MODERN    MACHINE    SHOP    TOOLS. 

the  quality  of  the  steel.  In  hardening,  a  coke,  charcoal  or  gas 
fire  should  be  used  for  heating  the  steel.  The  blast  should  be 
moderate  in  order  to  raise  the  temperature  uniformly  and  without 
overheating  corners  and  delicate  cutting  edges.  The  heat  should 
be  the  lowest  possible  at  which  the  steel  will  properly  harden. 
Too  high  a  heat  injures  the  quality  of  the  steel  and  increases 
the  strains  and  consequent  chances  for  cracking.  An  uneven 
heat  is  also  very  apt  to  produce  excessive  strains  and  cracks,  when 
the  steel  is  quenched. 

For  small  flat  pieces  the  heating  is  frequently  done  in  the  open 
flame  of  a  gas  or  charcoal  fire.  A  level  charcoal  fire  with  a  dis- 
tributed blast  is  much  used  for  heating  thin  work,  as  for  example, 
metal  saws,  gear  cutters  and  similar  work  which  can  be  laid  flat 
on  the  surface  of  the  fire.  A  fire  of  this  kind  is  also  suitable  for 
heating  small  round  work.  When  the  work  is  long  and  com- 
paratively small  in  diameter  a  muffler  is  often  used.  This  may 
consist  of  a  piece  of  pipe  buried  in  the  fire  and  heated  to  a  bright 
red.  The  work  is  held  in  the  center  of  the  pipe  and  by  constant- 
ly rotating  it  a  very  uniform  heat  is  obtained. 

The  heating  of  work  for  hardening  in  melted  lead  or  a  flux 
of  salt  and  cyanide  of  potassium  is  extensively  employed  by  many 
manufacturers  of  small  tools.  In  each  case  the  method  is  similar. 
A  deep  cast  iron  pot  of  from  four  to  six  inches  diameter  is  placed 
in  a  special  furnace  where  a  suitably  regulated  fire  can  be  main- 
tained under  and  around  it.  This  pot  is  filled  to  within  a  few 
inches  of  the  top  with  lead.  By  a  proper  regulation  of  the  fire 
the  temperature  of  the  lead  is  maintained  at  the  point  it  is  desired 
to  heat  the  steel  to.  To  prevent  the  oxidation  and  resulting  waste 
of  the  lead  its  surface  should  be  covered  with  powdered  charcoal. 
A  study  of  the  appearance  of  the  surface  of  the  lead  provides  a 
reliable  means  of  determining  the  proper  heat.  It  is  quite  pos- 
sible to  obtain  a  temperature  of  the  lead  sufficiently  high  to  injure 
a  high  carbon  steel ;  care  must  therefore  be  taken  in  the  matter  of 
regulating  the  heat. 

The  article  to  be  hardened  is  immersed  in  the  lead  and  allowed 
to  remain  until  it  has  acquired,  throughout  its  entire  body,  the 
same  temperature  as  the  lead.  It  is  evident  that  all  parts  of  the 
work  surface  are  subject  to  the  same  degree  of  heat,  which  insures 
the  greatest  uniformity  in  its  heating. 

After  heating,  the  hardness  is  obtained  by  quickly  cooling  the 
steel.  The  usual  method  is  to  plunge  it  into  cold  water,  brine  or 


HARDENING    AND    TEMPERING.  443 

oil,  immediately  after  taking  it  from  the  fire.  This  sudden  cool- 
ing of  the  steel  is  necessary,  and  the  success  of  tempering  depends 
very  largely  upon  the  manner  in  which  it  is  done.  The  shape  and 
character  of  the  work  must  in  every  case  determine  the  manner 
in  which  the  steel  is  presented  to  the  cooling  bath.  Salt  added  to 
the  water  in  which  the  quenching  is  performed  intensifies  the 
hardening  effect.  If  the  body  of  steel  is  large,  a  large  volume  of 
cooling  solution  is  necessary. 

When  the  work  is  of  a  bulky  character,  that  part  which  first 
enters  the  cooling  bath  is  quite  apt  to  harden  better  than  the  top, 
inasmuch  as  the  boiling  action  prevents  the  water  from  coming  in 
actual  contact  with  the  surface  longer  at  the  upper  parts  of  the 
work  than  at  the  lower.  For  this  reason,  on  heavy  work,  a  large 
jet  of  water  is  frequently  forced  against  the  upper  portion  of 
the  work. 

Cooling  in  oil  is  for  many  classes  of  work  considered  superior 
to  water  or  brine.  In  its  softer  action  and  more  rapid  conduction 
of  the  heat  from  the  steel,  lie  the  advantages  in  oil  quenching. 
Sperm  or  cottonseed  oils  are  those  usually  employed.  In  using 
the  fish  oils,  some  means  of  ventilating  that  will  carry  away  the 
disagreeable  odor  should  be  employed.  Springs  of  all  classes 
are  usually  hardened  in  oil. 

When  the  lead  bath  is  used  for  heating  more  or  less  of  the 
lead  and  its  dross  will  adhere  to  the  work  if  it  is  put  in  dry.  By 
covering  the  work  with  a  thin  coating  of  soft  soap  before  im- 
mersing it,  a  thin  charred  covering  will  form  over  the  surface  of 
the  steel  which  prevents  the  lead  from  adhering  to  it  when  re- 
moved from  the  bath.  By  first  plunging  the  work  into  a  brine 
solution  this  coating  is  removed,  leaving  a  clear  gray  surface  on 
the  work. 

When  the  workman  is  not  familiar  with  the  hardening  of  a 
particular  brand  of  steel  from  which  some  expensive  tool  is  made, 
it  is  usually  advisable  for  him  to  experiment  upon  a  small  piece 
from  the  same  bar  and  thus  determine  the  lowest  heat  at  which 
the  steel  will  properly  harden.  It  is  important  that  the  article 
hardens  on  the  first  heat  as  reheating  is  quite  apt  to  injure  the 
quality  of  the  steel  and  adds  to  the  possibility  of  loss  by  cracking. 

Having  hardened  the  work  to  a  degree  considerably  beyond 
that  required,  it  is  then  necessary  to  temper  it,  which  involves 
the  reduction  of  the  hardness  to  the  point  necessary  for  the  work 
required  of  the  tool.  The  tempering  of  steel  is  accomplished  by 


444  MODERN    MACHINE    SHOP    TOOLS. 

gradually  raising  its  temperature  until  the  hardness  has  drawn  or 
let  down  to  the  required  point,  when  plunging  the  steel  into  water 
lixes  the  hardness.  When  the  temperature  has  reached  about 
600  degrees  Fahrenheit  the  hardness  has  been  drawn  down 
through  the  several  points  at  which  cutting  tools  for  the  various 
uses  are  tempered.  If  the  rise  in  temperature  continues  past  this 
point  the  hardness  continues  to  disappear  in  proportion  to  the 
amount  of  heat  given  it.  When  a  red  heat  is  reached  it  has  lost 
all  the  hardness  given  it  in  the  hardening  process  and  is  again 
back  to  its  normally  soft  condition. 

The  correct  tempering  of  a  piece  of  hardened  steel  for,  any 
class  of  work  must  therefore  depend  upon  the  workman's  ability 
to  raise  the  temperature  to  the  proper  degree  before  cooling. 
This  he  accomplishes  by  one  of  two  methods;  first  by  actually 
measuring  the  temperature  with  a  thermometer  and  second,  by 
what  is  known  as  the  color  method.  Except  in  cases  where  tem- 
pering is  done  in  a  manufacturing  way  the  latter  method  is  the 
one  always  employed. 

An  understanding  of  the  colors,  the  corresponding  tempera- 
tures and  the  relation  between  color  and  hardness  are  quite 
necessary.  Lathe  and  planer  tools  are  given  a  hard  temper.  Their 
color  is  a  straw  yellow,  which  comes  at  a  temperature  of  460  de- 
grees. A  brown  yellow  at  500  degrees  is  used  for  milling  cut- 
ters, taps,  dies,  and  reamers.  Light  purple  at  530  degrees  is 
about  right  for  twist  drills  and  wood  working  tools  and  dark 
purple  at  550  to  a  dark  blue  at  570  degrees  is  usual  for  cold 
chisels,  screw  drivers,  and  wood  saws. 

In  determining  the  proper  temper  by  means  of  a  thermometer 
the  following  method  is  employed :  Take  for  example  the  tem- 
pering of  a  quantity  of  small  taps.  Having  been  properly  hard- 
ened they  are  placed  in  a  wire  basket  and  the  entire  mass  sus- 
pended in  an  iron  vessel  filled  with  sperm  oil.  The  vessel  is 
covered  with  a  closely  fitting  cover  having  a  hole  through  the 
top  sufficiently  large  to  permit  the  stem  of  a  thermometer,  which 
is  in  the  oil,  to  extend  through  for  reading.  As  the  tempera- 
tures required  are  considerably  below  the  boiling  point  of  mer- 
cury, a  mercurial  thermometer  having  the  necessary  range  may 
be  employed  for  determining  proper  temperatures.  It  is  neces- 
sary to  cover  the  oil  closely,  as  otherwise  it  would  flash  up  at 
the  high  temperatures  employed.  Heat  is  applied  to  the  bottom 
of  the  vessel  and  the  temperature  of  the  oil  and  the  articles  in  it 


HARDENING    AND    TEMPERING.  445 

gradually  raised  until,  in  the  present  example,  the  thermometer 
indicates  a  temperature  of  500  degrees.  In  order  to  obtain  a 
perfectly  even  temperature  in  the  oil  it  is  advisable  to  arrange 
for  some  means  of  stirring  it  while  the  heat  is  being  applied. 
The  basket  and  its  contents  are  taken  out  when  this  point  i» 
reached  and  immersed  in  cold  water  with  the  assurance  that  a 
uniform  temper  has  been  obtained  in  the  entire  batch. 

In  tempering  by  color,  the  article  after  being  hardened  is  made 
bright  by  grinding  or  buffing.  Taps  and  reamers  for  example 
are,  after  hardening  and  before  tempering,  ground  in  the  flutes, 
thus  leaving  bright  surfaces  to  show  the  run  of  the  color.  The 
article  is  then  held  over  the  fire,  being  constantly  turned  in  such 
a  manner  that  all  parts  are  equally  exposed  to  the  heat.  The 
raising  of  the  temperature  should  be  gradual  and  the  surface 
closely  wratched  for  the  first  show  of  color.  The  color  will  start 
with,  a  very  light  tinge  pf  yellow  which  gradually  changes  into 
a  straw  yellow  and  next  into  the  brownish  yellow.  If  it  is  a 
tap  or  a  reamer  it  is  quickly  immersed  in  cold  water  just  as  the 
yellow  blends  into  the  brown.  If  it  was,  for  example,  a  cold 
chisel,  the  colors  would  be  allowed  to  run  from  the  yellow  through 
the  purples  and  into  the  dark  blue. 

As  is  the  case  when  heating  for  hardening,  difficult  work, 
especially  if  long,  can  usually  be  heated  for  tempering  in  a  muffler 
to  very  good  advantage. 

An  excellent  method  of  heating  for  tempering  small  tools,  as 
taps,  reamers,  cutters,  etc.,  is  in  a  bath  of  sand.  A  suitable  tray 
covered  with  about  one  inch  of  pure  white  sand  supported  over  a 
series  of  gas  burners  is  employed.  By  first  burning  all  the  im- 
purities out  of  the.  sand  false  colors  will  not  be  shown  on  the 
articles  being  tempered.  The  article,  if  small  or  thin,  can  be 
laid  on  the  top  of  the  sand,  but  if  larger,  it  should  be  buried  .in 
it,  only  a  small  part  of  the  surface  being  exposed  to  show  the' 
starting  of  the  color. 

In  the  tempering  of  a  piece  of  steel,  the  strains  are  such  that 
the  form  of  the  article  usually  undergoes  a  change.  This  may 
occur  in  either  the  hardening  or  the  tempering  or  both.  In  such 
tools  as  milling  cutters  and  reamers  which  receive  their  final 
finishing  by  grinding  after  they  are  tempered  slight  changes  in 
form  are  not  troublesome.  With  long  taps,  drills,  formed  cut- 
ters, etc.,  it  becomes  a  more  serious  question.  Take,  for  ex- 
ample, a  stay  bolt  tap  two  feet  long.  Although  the  greatest  care 


MODERN    MACHINE    SHOP    TOOLS. 

is  exercised  in  tempering,  it  usually  comes  out  badly  bent.  In 
straightening  work  of  this  kind  it  is  necessary  to  heat  it  up 
very  nearly  to  its  temper  point,  place  it  between  a  pair  of  centers, 
revolve  it  quickly  by  drawing  the  hand  over  it  and  note  with  a 
piece  of  chalk  the  high  point  or  belly.  Place  it  with  the  belly 
down  and  by  means  of  a  lever  or  small  jack  having  a  quick  pitch 
screw,  spring  the  work  in  the  direction  opposite  to  its  curvature 
and  beyond  its  proper  position  an  amount  somewhat  greater  than 
its  temper  bend.  Hold  it  in  this  strained  position  for  a  few 
seconds,  remove  quickly  and  immerse  in  cold  water.  The  ex- 
perience gained  in  a  few  trials  will  usually  enable  the  operator  to 
successfully  straighten  work  of  this  character. 

As  a  general  rule  it  is  not  advisable  to  leave  tool  steel  long 
in  the  fire  as  ''soaking"  is  usually  injurious  to  its  structure.  Oc- 
casionally, however,  a  piece  of  steel  known  to  be  of  good  quality 
will  resist  hardening  properly  when  treated  by  the  regular  meth- 
ods. In  such  cases  it  can  usually  be  hardened  if  allowed  to  re- 
main in  an  even  fire  and  "soak"  for  a  considerable  length  of  time. 

When  a  hard  surface  and  soft  center  are  required,  as  is  often 
the  case  when  the  tool  must  stand  severe  strains  and  shocks,  it  is 
given  a  quick  surface  heat,  the  core  remaining  comparatively 
cool,  and  then  plunged  into  the  cooling  solution.  This  hardens 
the  surface  and  leaves  a  soft  strong  core.  Large  mandrels, 
punches,  dies  and  articles  of  that  class  are  usually  hardened  in 
this  manner. 

As  the  high  carbon  steels  harden  at  comparatively  low  heats 
they  should  never  be  given  a  high  heat  either  for  forging  or  hard- 
ening as  the  dangers  of  burning  them  are  great. 

Forged  articles,  as  lathe  tools  and  cold  chisels,  are  usually 
hardened  and  tempered  with  the  same  heat.  In  such  cases  only 
a  small  portion  at  the  cutting  edge  is  tempered.  It  is  heated 
for  a  considerable  distance  back  from  the  part  to  be  tempered 
and  the  heat  in  this  portion  is  used  in  drawing  to  temper  the 
cutting  portion.  For  example,  a  cold  chisel  which  should  be  tem- 
pered for  only  a  short  distance  back  from  the  point,  is  given  a 
proper  heat  for  hardening  at  the  point  and  this  heat  allowed  to 
run  back  two  or  three  inches.  In  quenching  only  the  point  for  a 
half  inch  or  so  back  is  immersed  and  held  until  the  red  has  nearly 
faded  out  of  the  heated  portion.  It  is  then  removed  and  the 
bit  brightened  up,  by  a  few  quick  strokes  over  its  surface  with 
•a  piece  of  emery  cloth,  sand  stone  or  any  grinding  material  at 


HARDENING    AND    TEMPERING.  447 

hand.  The  operator  then  watches  for  the  color,  the  heat  in  the 
balance  of  the  tool  being  sufficient  to  draw  the  point.  The  straw 
colors  will  start  first  and  move  toward  the  point;  these  will  be 
quickly  followed  by  the  purples  and  the  blue,  and  just  as  the 
required  color  reaches  the  point  the  tool  is  plunged  in  the  water. 
When  too  much  heat  remains  in  the  tool  after  the  hardening  of 
the  point,  the  temper  draws  too  fast  and  the  point  must  be  im- 
mersed a  second  time  to  check  the  drawing,  as  it  would  not  do 
to  immerse  the  whole  tool  while  so  much  heat  remains  in  it.  On 
the  other  hand  if  too  little  heat  remains  with  which  to  draw  the 
temper,  it  will  be  necessary  to  draw  in  the  open  fire  as  above 
explained. 

What  are  known  as  tungsten  or  self-hardening  steels  have 
come  into  very  general  use  for  machine  shop  cutting  tools  which 
require  no  machine  work  upon  them  and  little  or  no  forging. 
These  steels  are  produced/  by  adding  several  per  cent  of  the 
metal  tungsten  to  the  carbon  steel.  This  makes  a  steel  possess- 
ing great  hardness  without  the  necessity  of  tempering.  It  is 
very  "short"  when  heated  and  requires  great  care  and  skill  in 
forging.  It  is  usually  used  in  special  holders  and  ground  to 
shape  without  the  necessity  of  forging.  After  heating  for  forg- 
ing the  steel  must  be  allowed  to  cool  in  the  air  as  immersion  in 
water  is  sure  to  crack  it.  It  must  be  nicked  on  an  emery  wheel 
and  broken  to  required  lengths,  as  it  cannot  be  cut  when  cold. 

The  demand  for  high  cutting  speeds  and  the  comparatively 
recent  introduction  of  high  speed  cutting  steels  to  meet  this  re- 
quirement is  creating  a  vast  amount  of  interest.  These  steels 
are,  unlike  tungsten  steel,  capable  of  annealing  and  consequently 
can  be  used  for  making  tools  of  finer  class,  as  milling  cutters, 
reamers,  etc.  In  some  recent  experiments  by  the  author  with 
"Novo"  air-hardening  steel,  cutting  speeds  as  high  as  no  feet 
per  minute  at  coarse  feed  and  moderate  cuts  on  mild  steel  forging 
without  lubrication,  were  successfully  maintained.  Although  the 
cutting  edge  quickly  drew  to  a  dark  blue  it  held  its  keenness  for 
an  unusual  length  of  time.  It  is  quite  evident  that  for  heavy 
roughing  work  these  steels  are  remarkably  well  adapted  and  that 
the  rigidity  and  ordinary  spindle  speeds  of  standard  engine^ 
lathes  are  not  sufficient  for  its  most  effective  use. 

In  forging  the  "Novo"  steel  it  is  at  all  temperatures  other 
than  a  white  heat  "hot  short"  and  crumbles  or  crushes  away.  It 
cannot  be  burnt  and  for  forging  and  hardening  must  be  given 


448  MODERN    MACHINE    SHOP    TOOLS. 

a  uniform  white  welding  heat.  When  thus  heated,  for  harden- 
ing, it  is  placed  immediately  under  the  strongest  and  coldest  air 
blast  available  and  left  until  quite  cold.  It  is  not  drawn  or 
tempered  after  hardening.  These  steels,  although  extremely  hard, 
possess  reasonable  strength.  It  is  advisable,  however,  for  heavy 
work  to  use  as  large  a  bar  as  possible,  not  only  because  better 
support  to  the  cutting  edge  can  be  had,  but  because  the  large 
body  of  steel  conducts  away  the  heat  caused  by  the  cutting  much 
more  rapidly  than  can  a  small  tool. 

The  case  hardening  of  iron  and  mild  steel  is  a  process  where- 
by the  surface  of  the  work  is  converted  into  tool  steel  and  hard- 
ened. This  is  accomplished  by  heating  the  work  in  contact 
with  a  material,  rich  in  carbon,  which  gives  up  its  carbon  to  the 
work. 

When  large  numbers  of  pieces  are  to  be  case  hardened  they 
are  packed  in  an  iron  box  with  granulated  rawbone  and  fine 
charcoal  mixed  in  about  equal  proportions.  For  the  rawbone 
may  be  substituted  bone  black,  charred  leather  or  some  one  of 
the  various  special  preparations  for  this  work.  The  box  is  sealed 
with  an  iron  cover  and  fire  clay  at  the  joints  to  exclude  the  air 
and  prevent  the  escape  of  the  gases  as  far  as  possible.  It  is  then 
placed  in  the  furnace  and  allowed  to  slowly  heat  up  to  a  low  red 
heat,  at  which  temperature  it  is  maintained  for  a  length  of  time 
depending  upon  the  depth  it  is  desired  to  convert  the  surface  of 
the  work  into  tool  steel.  Under  favorable  conditions  the  surface 
will  harden  to  a  depth  of  1-32  inch,  by  heating  about  two  hours; 
1-16  can  be  obtained  in  from  five  to  six  hours  and  by  heating 
for  eighteen  or  twenty  hours,  a  hardened  surface  as  thick  as  ^4- 
inch  can  be  obtained. 

After  heating  the  contents  of  the  box,  it  is  dumped  into  a  tank 
of  cooling  water  preferably  of  considerable  depth,  as  the  articles 
should  be  well  cooled  before  they  reach  the  bottom.  By  allowing 
the  articles  to  fall  a  short  distance  through  the  air  before  strik- 
ing the  water,  the  coloring  of  the  surface  will  be  improved. 

When  only  a  few  pieces  are  to  be  treated,  they  may  be 
heated  in  an  open  fire  to  a  bright  red  ;  the  surfaces  to  be  hard- 
ened then  covered  with  cyanide  of  potassium  and  again  heated 
before  cooling  in  the  water.  The  thickness  of  the  case  hardened 
surface  thus  obtained  is  quite  thin.  By  several  applications  of 
the  cyanide  it  can  be  made  sufficiently  thick  for  most  require- 
ments. 


HARDENING    AND    TEMPERING.  449 

Another  and  very  satisfactory  method  is  to  melt  in  a  black  lead 
crucible,  equal  parts  of  cyanide  of  potassium  and  fine  salt. 
Bring  this  up  to  a  bright  red  heat  and  immerse  the  articles  to  be 
hardened  in  it,  leaving  for  a  length  of  time  depending  on  the  de- 
gree of  hardness  required.  Five  to  ten  minutes  will  give  a  thick- 
ness sufficient  for  all  ordinary  requirements. 

When  finely  mottled  surfaces  are  desired,  the  work  should  be 
polished  and  thoroughly  cleaned  before  treating.  The  blowing  of 
air  through  the  cooling  water  at  the  time  the  work  is  cooled  will 
add  much  to  the  beauty  of  the  markings  on  its  surface. 


CHAPTER   XXX. 

FASTENINGS. 

The  term  "fastening"  applies  to  those  devices  used  by  the 
machinist  for  holding  together  in  their  relative  positions  the 
various  elements  that  make  up  a  machine.  Their  importance  in 
mechanical  work  cannot  be  overestimated,  and  a  brief  description 
of  the  more  important  cases  seems  advisable. 

With  few  exceptions,  all  threaded  fastenings  use  the  sharp 
V  or  United  States  standard  form  of  thread.  In  Fig.  585  are 
shown  the  three  forms  of  machine  bolts  most  used.  The  manu- 
facturers of  machine  bolts  have  adopted  the  United  States  stand- 
ard form  of  thread  and  as  a  consequence  these  bolts  run  reason- 
ably close  to  size,  but  a  trifle  small.  A  y$  bolt,  for  example,  will 
pass  through  a  y%  drilled  hole.  The  square  head  and  nut  bolt  as 
shown  at  A  is  most  used  on  general  work.  When  the  nut  comes 
in  a  place  where  it  is  difficult  to  get  at  it  with  a  wrench,  the 
hexagon  nut  is  substituted  for  the  square.  At  B  the  bolt  has 
both  hexagon  head  and  nut,  presenting  a  more  finished  appear- 
ance. The  snap  or  round  head  machine  bolt  is  shown  at  C.  It 
differs  from  the  others  only  in  its  form  of  head.  Carriage  bolts 
are  similar  as  to  diameter  and  form  of  thread  to  the  machine  bolt 
shown  at  C  with  the  exception  of  a  square  under  the  head  which 
prevent*  them  from  turning  when  used  in  wood.  The  length  of 
this  square  section  is  approximately  equal  to  the  diameter  of  the 
bolt. 

On  square  and  hexagon  head  machine  bolts,  the  thickness  of 
the  head  is  %  the  diameter  of  the  bolt  and  the  thickness  of  the 
nut  is  \y%  the  diameter.  The  width  of  the  head  and  nut  be- 
tween flats  is  1^4  the  diameter  of  the  bolt  in  both  the  hexagon 
and  square.  The  width  from  angle  to  angle  on  the  hexagon  is 
two  times  the  bolt  diameter.  A  table  of  weights  and  dimensions 
of  machine  bolts  is  given  in  Chapter  XXXIV. 

Turned  machine  bolts,  commonly  known  as  coupling  bolts,  are 
much  used  for  holding  together  machine  and  engine  parts.  In 
such  cases  they  fit  closely  in  reamed  holes. 

Machine  bolts  with  specially  formed  heads  and  nuts  are  fre- 
quently used.  As  they  are  not  regularly  carried  in  stock  by  the 


FASTENINGS. 


451 


manufacturers  and  must  be  made  up  to  order,  any  desired  form 
may  be  had. 

When  the  character  of  the  work  is  such  that  one  of  the  parts 
that  are  being  secured  together  can  be  tapped,  a  stud  bolt  or  cap 
screw  may  be  used.  In  Fig.  586  at  A  is  shown  the  standard 
form  of  milled  stud.  The  short  thread  is  usually  made  slightly 
larger  than  the  long  one,  as  it  is  intended  to  fit  closely  the  tapped 
hole  in  the  work.  The  stud  when  set  extends  above  the  surface 
an  amount  sufficient  to  receive  the  work  and  a  nut  on  the  outside. 


FIG.  585. 


FIG.  587. 


At  B  and  C  are  shown  two  forms  of  special  collar  studs  used  only 
on  special  work.  In  Fig.  587  is  shown  a  simple  device  for  set- 
ting studs.  A  piece  of  hexagon  steel  with  a  tapped  hole  through 
it  as  shown,  is  screwed  on  the  end  of  the  stud  and  the  special  set 
screw  tightened  against  the  end  of  the  stud.  The  set  screw 
should  be  cupped  slightly  as  shown,  and  hardened.  It  is  also  ad- 
visable to  case  harden  the  body.  By  using  two  wrenches  the 
device  is  readily  removed  after  the  stud  has  been  set. 

It  is  frequently  necessary  to  lock  the  nuts  on  bolts  and  studs 
to  prevent  them  from  working  loose.     The  use  of  two  nuts,  as 


45^ 


MODERN    MACHINE    SHOP    TOOLS. 


shown  in  Fig.  588,  at  A,  is  a  very  common  method.  The  thinner 
nut  is  called  a  lock  or  check  nut  and  is  usually  one-half  the 
bolt  diameter  in  thickness.  The  check  nut  is  usually  put  on 
the  outside;  a  better  distribution  of  the  strains,  however,  is  ob- 
tained when  the  thin  nut  is  placed  on  the  inside.  This  arrange- 
ment of  nuts  while  not  absolutely  proof  against  their  working 
loose,  can  usually  be  relied  upon.  By  allowing  the  bolt  to  ex- 
tend through  the  nut  an  amount  sufficient  to  permit  drilling  a 
hole  and  inserting  a  cotter  key,  as  shown  at  B,  a  most  satisfac- 
tory safeguard  against  loosing  the  nut  is  obtained.  The  cotter 
key  in  connection  with  the  jam  nut  is  perfectly  safe. 

Devices  of  the  character  of  the  one  shown  in  Fig.  589  are 


A.  B. 

FIG.  588. 


occasionally  used  in  connection  with  standard  nuts.  More  often,, 
however,  a  special  nut  having  a  notched  rim  is  used  in  connection 
with  a  dog  to  engage  the  notches  and  secured  to  the  body  of  the 
work. 

Cap  screws  are  similar  to  coupling  bolts  without  nuts.  In 
Fig.  590  are  shown  three  styles ;  at  A,  a  square  head ;  at  B,  a 
hexagon  head,  and  at  C,  a  form  known  as  a  tap  bolt  which  is 
threaded  close  under  the  head.  When  cap  screws  are  used  in 
places  where  they  must  often  be  turned,  they  are  usually  of  the 
forms  shown  in  Fig.  591  and  known  as  collar  cap  screws. 

Cap  screws  with  slotted  heads  for  a  screw  driver,  are  shown 


FASTENINGS. 


453 


in  Fig-.  592 ;  the  flat  head  at  A ;  the  round  or  button  head  at  B, 
and  the  fillister  head  at  C.  These  are  known  as  machine  screws 
when  of  machine  screw  diameter  and  threads. 

Set  screws  are  made  of  steel  and  tempered  or  of  iron  and 
case  hardened.  They  form  a  convenient  and  largely  used  means 
of  securing  pulleys,  collars,  etc.,  to  shafting,  and  in  their  headless 


FIG.  590. 


FIG.  591 


forms  for  holding  liners  and  other  machine  parts.  Set  screws 
are  not  well  suited  to  the  holding  of  pulleys  that  must  transmit 
much  power,  as  they  do  not  get  much  bearing  on  the  shaft  and 
as  a  result  are  very  apt  to  slip.  The  standard  form  of  set  screw 
is  shown  in  Fig.  593,  as  is  also  the  headless  pattern.  What  are 
known  as  low  head  or  collar  set  screws  have  square  heads  of 


about  one-half  the  height  of  the  regular  head.  In  this  figure  are 
also  shown  the  various  forms  of  points  used  on  set  screws.  A 
and  B,  the  cupped  and  ovai  points,  are  regular  patterns.  The 
flat  point  C,  the  cone  point  D,  and  the  pivot  point  E  are  specials. 
Studs,  cap,  and  set  screws  are  regularly  made  with  both  the 


454 


MODERN    MACHINE    SHOP    TOOLS. 


sharp  V  and  United  States  standard  threads ;  unless  the  latter  is 
specified,  orders  are  always  filled  with  V  threads. 

Square  and  hexagon  nuts  may  be  had  either  hot  or  cold  press- 
ed, commonly  known  as  black  and  bright.  The  cold  pressed  nuts 
are  those  usually  used  on  machine  and  engine  work.  A  plain 
nut,  tapped  and  faced  on  the  work  side  meets  the  necessities  of 
any  case.  It  is  not,  however,  when  applied  to  well-finished  work, 
in  keeping  in  appearance.  It  is  therefore  usual  to  use  what  are 
termed  semi-finished,  finished  or  finished  and  case  hardened  nuts 
on  good  work.  A  semi-finished  nut  is  faced  bottom  and  top  and 
chamfered  on  the  top.  A  finished  nut  has  its  faces  buffed  or 


FIG.  594. 

ground  smooth  in  addition  to  the  facing,  and  the  case  hardened 
nut,  as  its  name  indicates,  is  hardened  after  being  finished. 

Keys  and  feathers  are  much  used  in  machine  construction  in 
the  fastening  of  the  parts  to  shafts.  In  Fig.  594  are  shown  the 
three  forms  of  keys  most  used.  The  round  key,  shown  at  A, 
is  used  in  places  where  little  power  is  to  be  transmitted  and  on 
light  work  only.  A  small  hole  drilled  half  in  the  hub  and  half 
in  the  shaft  receives  the  round  key,  which  is  usually  not  tapered 
and  driven  firmly  in.  By  tapping  the  hole,  a  headless  screw  can 
be  substituted  for  the  round  key.  This  not  only  provides  a  means 
for  removing  if  necessary,  but  prevents  the  possibility  of  any 


FASTENINGS.  455 

motion  in  the  direction  of  the  shaft's  length.  Keys  of  this  kind 
can  be  properly  applied  only  when  the  end  of  the  shaft  and  hub 
are  in  the  same  plane.  When  the  hub  and  shaft  are  of  different 
materials,  as  is  usually  the  case,  difficulty  is  experienced  in  mak- 
ing" the  drill  follow  the  joint,  as  it  will  tend  to  crowd  toward  the 
softer  metal. 

Where  the  strains  transmitted  are  moderate,  the  flat  key 
shown  at  B  may  be  employed.  As  the  flat  on  the  shaft  can,  if 
necessary,  be  filed,  this  forms  a  most  convenient  method  ot  key- 
ing after  a  shaft  is  in  place.  The  width  of  the  key  should  be 
from  one-quarter  to  one-third  the  diameter  of  the  shaft.  If  the 
key  way  is  tapered  in  the  hub  the  key  should  have  the  same  taper 
and  can  be  driven  firmly  to  its  seat.  If  the  key  way  is  straight 
it  is  necessary  to  use  two  set  screws  over  the  key. 

The  flat  key  sunk  in  the  shaft,  as  shown  at  C,  is  the  most 
reliable  and  consequently  most  used.  It  is  a  tapered  key  fitting 
closely  in  the  sides  and  driven  to  a  tight  top  and  bottom  fit.  By 
using  a  straight  key  way  with  set  screws  over  each  end  the  key 
may  be  made  straight. 

Practice  as  to  the  taper  and  dimensions  of  keys  is  somewhat 
at  variance.  Good  practice,  however,  indicates  the  use  of  3-16 
of  an  inch  taper  per  foot  with  a  width  of  key  equal  to  one-quarter 
the  shaft  diameter  and  a  thickness  equal  to  one-sixth  the  shaft 
diameter.  For  shafting  a  width  equal  to  one-quarter  the  diameter 
and  a  thickness  1-16  of  an  inch  less  than  the  width  is  much  used. 

Tapered  keys  are  little  used  by  machine  tool  builders  owing 
to  their  tendency  to  throw  the  parts  out  of  true,  due  to  the  radial 
strain.  For  such  work  straight  square  keys  fitting  neatly  on  the 
sides  but  loose  top  and  bottom  are  much  used.  Straight  keys 
should  be  set  one-half  their  thickness  in  the  shaft  and  the  depth 
of  key  seat  should  be  measured  from  the  sides,  not  the  center, 
With  tapered  keys  the  depth  of  key  way  in  shaft  should  be  one- 
half  the  thickness  of  the  key  at  its  middle  section.  A  recom- 
mended practice  is  that  the  depth  of  key  way  in  shaft  should  equal 
two-fifths  the  thickness  of  the  key  at  its  thick  end. 

Feather  keys  are  much  used  by  machine  tool  builders.  They 
are  usually  of  a  thickness  greater  than  their  width  and  are  not 
fitted  tight  top  and  bottom.  When  fitted  in  this  manner  the  key 
does  not  hold  against  motion  along  the  shaft,  consequently  very 
close  fits  between  shaft  and  bore  are  necessary. 

Sliding   feathers    are   those    which   are    doweled    in    the   hub 


456 


MODERN    MACHINE    SHOP    TOOLS. 


where  a  sliding  fit  of  the  spindle  through  the  hub  is  required,  as 
with  drilling  machine  spindles,  feed  rods,  etc.  Feathers  of  this 
kind  should  be  long  in  order  to  resist  wear,  and  as  they  must  fit 
the  spline  in  the  spindle  freely  they  drive  from  the  hub  seat  and 
should  therefore  have  a  close  deep  bearing  in  this  seat.  It  is 
usual  to  make  sliding  feathers  of  a  thickness  equal  to  one  and 


FIG.  595. 

one-half  the  width  with  one-half  their  thickness  in  the  hub. 
When  necessary  it  is  of  course  possible  to  reverse  the  conditions 
and  dowel  the  feather  in  the  shaft,  the  hub  sliding  over  it. 

The  Woodruff  system  of  keying,  as  largely  used  by  machine 
tool  builders,  is  illustrated  in  Figs.  595  and  596.  The  key  is  a 
semi-circular  disc  of  soft  steel  of  the  required  thickness.  The 


FIG.  596. 

cutter  for  making  the  seats  is  shown  in  Fig.  488.  It  is  dropped 
the  proper  depth  in  the  shaft  to  receive  the  key  as  shown.  When 
a  long  key  is  required  two  or  more  of  the  keys  are  placed  end  to 
end,  as  shown  in  Fig.  595.  When  used  as  a  tapered  key,  as 
shown  in  Fig.  596,  they  adapt  themselves  perfectly  to  the  taper 


FASTENINGS. 


457 


in  the  hub  and  thus  overcome  the  danger  of  cocking  the  work  as 
with  the  flat  tapered  key  when  the  tapers  do  not  exactly  corres- 
pond. 

When  taper  keys  are  used  in  places  where  there  is  a  possibility 
of  having  to  remove  them  some  provision  must  be  made  for  either 
drawing  or  drifting  them.  If  the  key  way  is  sufficiently  long 
and  the  back  end  of  the  hub  can  be  gotten  at  the  key  can  be  drifted 
out,  otherwise  some  form  of  head  must  be  provided  on  the  key 
to  make  it  possible  to  draw  it. 

In  Fig.  597  is  shown  the  Morton  gib  head  key  and  the  method 


of  drawing  it.  The  under  cut  head  gives  the  end  of  the  pinch 
bar  a  hold  and  prevents  its  slipping  off.  The  stepped  fulcrum 
blocks  shown  insure  a  square  pull  on  the  key.  In  this  manner 
gib  head  keys  can  be  safely  drawn.  The  driving  of  a  wedge  be- 
tween the  hub  and  the  head  of  the  key  injures  the  head  and  is 
very  apt  to  bend  the  key.  Two  wedges  of  equal  angle  introduced 
from  opposite  sides  and  driven  equally,  answers  very  well.  As 
they  tend,  however,  to  bend  the  head  toward  the  center  of  the 
shaft,  a  heavy  weight  should,  if  the  key  comes  hard,  be  held 
under  the  head. 

Keys  should  always  be  well  oiled  before  driving  them  home. 


458 


MODERN    MACHINE    SHOP    TOOLS. 


In  Fig.  598  is  shown  a  taper  pin.  They  are  made  in  sizes 
from  No.  o  to  No.  10,  varying  in  length  from  y\  of  an  inch  to  6 
inches  and  in  diameter  from  approximately  5-32  to  23-32  at  the 
large  end.  They  fit  holes  reamed  with  the  standard  taper  pin 
reamers  and  are  much  used  by  machinery  builders  for  securing 
collars,  gears,  couplings,  etc.  They  can  be  easily  removed  and 
when  again  put  back  it  is  with  the  absolute  certainty  that  the 
parts  are  back  in  their  exact  relative  positions.  They  are  not, 
however,  suited  to  the  transmitting  of  heavy  loads. 

The  cotter  pin  or  key,  Fig.  599,  is  but  little  used  for  purposes 
other  than  those  illustrated  in  Fig.  588. 

Rivets  make  the  simplest  form  of  fastening.  They  are,  how- 
ever, permanent  fastenings,  which  can  only  be  removed  by  cutting 


FIG.  598. 


FIG.  599. 


FIG.  600. 

»ff  the  head.  Rivets  are  little  used  for  purposes  other  than  the 
holding  together  of  metal  plates.  They  are  made  of  soft  tough 
steel  or  iron,  steel  rivets  being  most  used  on  the  heavier  steel 
plate  work.  Good  rivets  should  stand  riveting  up  cold,  without 
cracking,  a  method  most  used  on  light  work.  For  heavy  plates, 
as  used  in  boiler  and  structural  steel  work,  the  rivets  are  of  the 
forms  shown  in  Fig.  600  and  are  set  hot. 

Riveted  joints  are  of  two  kinds,  lap  and  butt  joints.  These 
are  shown  at  A  and  B,  Fig.  601.  In  the  lap  joint  the  plate  edges 
lap  over  each  other,  while  in  the  butt  joint  the  edges  come  square- 
ly against  each  other  and  a  cover  strip  is  placed  over  the  joint 
and  riveted  to  each  edge. 

A  single  riveted  joint  is  one  in  which  a  single  row  of  rivets 
are  used.  The  lap  and  butt  joints  shown  in  Fig.  60 1  are  examples 


FASTENINGS. 


45? 


of  single-riveted  joints.  When  two  lines  of  rivets  are  used  it 
becomes  a  double  riveted  joint  and  three  lines  a  triple  riveted 
joint.  A  covered  lap  joint  is  shown  in  Fig.  602.  A  cover  plate 


ggg 

^^^ 

^ssss^s 

^ 

V_ 

_/ 

FIG.  601. 


FIG.  602. 


is  flanged  and  riveted  over  the  joint  as  shown.  The  lap  joint 
rivets  pass  through  the  cover  strip  which  is  also  riveted  to  the 
plates  back  of  the  joint.  A  double  cover  butt  joint  is  shown  in 
Fig.  603.  This  joint  brings  the  rivets  in  double  shear. 


460 


MODERN    MACHINE    SHOP    TOOLS. 


Rivet  holes  are  punched,  or  drilled.  The  latter  method  is 
much  the  more  desirable,  but  owing  to  its  greater  cost,  is  not  so 
extensively  used  as  punching.  In  the  punching  of  rivet  holes 
the  metal  around  the  hole  is  injured  by  the  pressure  of  the 
punch  and  as  the  holes  must  be  laid  out  separately  in  each  sheet 


FIG.  603. 


FIG.  604. 

it  is  difficult  to  make  them  match  properly.  In  drilling,  both 
plates  are  usually  drilled  together  and  the  metal  is  not  injured 
in  any  way. 

By  punching  holes  somewhat  smaller  than  the  required  size 
and  reaming  them  out,  the  objection  to  punching  is  largely  over- 


FASTENINGS. 


461 


come.  If  the  plate  is  thick  the  edge  after  punching  should  be 
thoroughly  annealed.  The  use  of  a  drift  pin  in  rivet  holes  to 
bring  them  fair  is  very  objectionable  as  it  strains  the  plate,  fre- 
quently cracking  it.  In  the  drilled  holes  the  sharp  edges  left  are 
objectionable  and  should  be  slightly  rounded  for  best  results. 

Rivets  are  usually  set  hot  as  they  fill  the  holes  better  and  due 
to  their  contraction  in  cooling  draw  the  plates  very  firmly  to- 
gether. In  cases  where  the  rivets  are  long,  it  is  usually  necessary 
to  cool  the  heads  before  riveting  them,  as  otherwise  the  excessive 
amount  of  contraction  is  quite  apt  to  break  the  rivet.  It  is  most 
important  in  all  cases  that  the  amount  of  plate  lap  and  the  size 
and  pitch  of  rivets  be  properly  proportioned. 

The  strength  of  a  riveted  joint  depends  largely  upon  the  man- 
ner in  which  it  is  put  together.  When  properly  designed  and  put 


FIG.  605. 

together,  single-riveted  joints  will  average  from  50  to  55  per  cent 
of  the  plate  strength  and  double  riveted  joints  from  65  to  70  per 
cent. 

A  stay  bolt  is  a  piece  of  iron  or  steel  threaded  its  entire  length 
and  used  to  support  parallel  surfaces  in  boilers  which  are  com- 
paratively close  together.  By  means  of  a  long  stay  bolt  tap,  the 
holes  in  the  plates  are  tapped  together,  the  bolt  is  then  screwed 
through  the  plates,  cut  off  and  riveted  over,  as  shown  in  Fig. 
604.  When  the  plates  are  too  far  apart  to  permit  the  use  of 
threaded  stay  bolts,  some  other  form  of  stay  must  be  used.  The 
diagonal  stay,  Fig.  605,  is  frequently  used.  This  braces  the  flat 
end  to  the  shell  of  the  boiler.  The  feet  are  riveted  to  end  and 
shell  and  the  rod  connecting  them  is  of  the  proper  size  to  carry 
the  load. 


462 


MODERN    MACHINE    SHOP    TOOLS. 


When  the  diameter  of  the  shell  is  great,  the  feet  are  attached 
to  both  ends,  and  the  tie  rods  run  the  entire  length  of  the  boiler. 
When  a  number  of  such  stays  are  used  in  a  boiler  they  must  be  of 
the  same  length  as  otherwise  an  excessive  strain  is  thrown  on  the 
short  ones. 

In  many  cases  flat  surfaces,  as  for  example,  the  crown  sheet 


FIG.  606. 


of  a  fire  box,  are  supported  by  arch  or  girder  stays.  Such  a  stay 
is  shown  in  Fig.  606.  The  ends  of  the  stays  are  supported  on 
the  sides  of  the  fire  box  and  the  crown  bolts  shown  support  the 
-crown  sheet  against  the  downward  pressure. 


CHAPTER  XXXI. 

GEARING. 

The  term  gearing,  although  a  general  one  covering  all  means 
of  transmitting  motion,  is  more  especially  applied  to  wheel  gear- 
ing in  which  motion  is  transmitted  from  one  shaft  to  another  by 
means  of  toothed  wheels. 

Two  perfectly  smooth  rimmed  wheels  rolling  together  consti- 
tute a  geared  pair,  commonly  known  as  friction  gears  inasmuch 
as  the  one  drives  the  other  by  friction.  When  the  force  trans- 
mitted is  in  excess  of  the  frictioned  resistance,  slipping  occurs 
and  consequently  a  fixed  relationship  between  the  axes  of  the  two 
gears  can  not  be  maintained.  Such  a  pair  of  wheels  are  shown  in 
Fig.  607,  A  and  B. 

In  general  practice  frictional  gearing  is  not  extensively  used. 
It  is  frequently  found  in  mill  and  hoisting  work  and  more  especial- 
ly in  gears  for  reversing  purposes.  This  class  of  gearing  should 
be  very  carefully  made.  The  wheels  must  be  round  and  the  sur- 
faces as  true  and  smooth  as  possible.  At  least  one  of  each  pair 
should  have  a  soft  surface  as  of  wood,  leather  or  paper.  This 
should  be  the  driving  wheel,  the  driven  having  an  iron  face,  as 
in  the  case  of  any  slippage,  the  wear  on  the  soft-faced  driver  will 
be  equal  at  all  points  on  its  surface  and  it  will  tend  to  retain  its 
original  round  condition.  If  on  the  other  hand  the  iron  faced 
wheel  is  the  driver  and  the  soft  faced  wheel  for  any  reason  should 
stop,  the  driver  would  quickly  wear  a  concave  spot  in  the  soft 
cover  of  the  driven  wheel. 

If  we  assume  the  wheels  of  Fig.  607  of  the  same  diameter  and 
rolling  together  without  any  slip,  a  point  on  the  rim  surface  of 
one  travels  at  the  same  rate  of  speed  as  any  point  on  the  rim  of 
the  other,  and  the  distance  that  these  points  travel  in  the  unit  of 
time  is  called  the  "linear  velocity." 

The  rate  at  which  this  point  measures  angles  is  termed  its 
"angular  velocity."  Thus  with  wheels  A  and  B,  the  linear  and 
angular  velocities  are  the  same.  If  we  substitute  for  B  another 
wheel  C  of  one-half  the  diameter  of  A,  the  linear  velocity  of  any 
point  on  its  circumference  must  still  equal  the  linear  velocity  of 
B,  but  its  rate  of  measuring  angles  is  double  that  of  B  consequent- 


464 


MODERN    MACHINE    SHOP    TOOLS. 


ly  its  angular  velocity  is  doubled.  Considering  360  degrees  as 
the  angular  unit,  we  can  assume  it  in  terms  of  revolutions,  using 
the  same  unit  of  time  as  before. 

With  the  smooth  wheel  surfaces,  these  exact  relationships 
could  not  be  maintained.  If,  however,  teeth  are  formed  on  the 
surfaces  of  the  wheels  of  such  a  form  that  they  can  still  rotate  as 


FIG.  607. 


FIG.   608. 

above  without  the  possibility  of  slipping,  we  have  a  pair  of  gears 
the  velocity  ratios  of  which  can  be  absolutely  determined.  In 
order,  however,  that  the  linear  velocity  of  the  toothed  gears  are 
the  same  for  all  portions  of  their  revolution,  it  is  necessary  that 
they  be  provided  with  teeth  of  proper  outline.  If  such  is  not  the 
case,  the  motion  of  the  driven  gear  will  be  of  an  irregular  char- 
acter, a  variation  in  velocity  occurring  for  each  tooth. 


GEARING.  465 

All  gears  have  an  imaginary  circle  called  the  "pitch  circle" 
which  corresponds  to  the  circumferences  of  the  wheels  shown  in 
Fig.  607  and  are  the  circles  which  would,  if  the  tops  of  the  teeth 
were  cut  off,  roll  together  with  the  same  angular  velocity  as  did 
the  gears.  This  circle  is  shown  in  Fig.  608.  That  part  of  the 
tooth  outside  of  the  pitch  circle  is  called  the  "addendum"  and  the 
portion  inside  is  called  the  "land,"  or  "dedendum."  That  part 
of  the  tooth  outline  outside  of  the  pitch  circle  is  called  the  "face" 
and  that  part  inside  of  the  pitch  circle  the  "flank."  The  "pitch 
point"  is  where  the  "face"  and  "flank"  join  at  the  "pitch  circle." 
The  "root  circle"  passes  through  the  bottoms  of  the  teeth  and 
the  "addendum  circle"  passes  through  the  tops  of  'the  teeth.  The 
diameter  of  the  "addendum  circle"  is  the  whole  or  blank  diameter 
of  the  gear. 

The  "circular  pitch"  of  gear  teeth  is  the  distance  measured  on 
the  pitch  circle  from  the  pitch  point  of  one  tooth  to  the  corres- 
ponding point  on  the  next  tooth.  By  "diametral  pitch"  is  meant 
the  number  of  teeth  in  the  gear  per  inch  of  its  pitch  diameter. 
Thus  if  the  pitch  diameter  of  a  gear  is  10  inches  and  there  are 
80  teeth  in  the  gear,  the  diametral  pitch  would  be  8.  The  pitch 
circumference  is,  in  the  same  case,  10X3.1416  =  31.416  inches 

31.416 
and  -  =  -3926  --  the  circular  pitch.     In  any  case  3.1416 

80 

X  the  diameter  divided  by  the  number  of  teeth  equals  the  circular 
pitch  and  as  the  diameter  divided  by  the  number  of  teeth  equals 


-  ,    the   simple   expression  -  =   the   circular 
diametral    pitch  P 

pitch  where  P  =  the  diametral  pitch.  Nearly  all  gear  calcula- 
tions are  now  made  in  terms  of  the  diametral  pitch.  In  the  mak- 
ing of  patterns,  the  work  is  usually  based  on  the  circular  pitch, 
which,  however,  is  deduced  from  the  diametral  pitch  as  above. 
In  the  cutting  of  racks  it  is  necessary  to  know  the  circular  pitch 
in  order  to  properly  space  for  the  teeth. 

one    inch 
The  addendum  equals  on  standard  gear  teeth  - 

diametral    pitch 

=  in  above  case  Y%  inch.  This  gives  for  the  whole  diameter,  the 
pitch  diameter  -j-  l/4  inch  or  twice  the  addendum.  The  flank  of  the 
tooth  equals  the  face,  thus  giving  for  the  working  depth  twice 


466  MODERN    MACHINE    SHOP    TOOLS. 

the  addendum  or  two  diametral  pitches.  Bottom  clearance  is 
usually  made  equal  to  i-io  of  the  thickness  of  the  tooth  on  the 
pitch  line. 

The  thickness  of  the  tooth  and  width  of  the  space  measured 
on  the  pitch  line  are  for  carefully  cut  gears  practically  equal. 
When  the  teeth  are  cast  and  consequently  not  perfect  as  to  form, 
it  is  necessary  to  make  the  tooth  slightly  thinner  than  the  space. 
This  difference  is  called  the  back  lash. 

In  a  pair  of  gears  the  distance  between  their  axes  is  equal  to 
the  sum  of  their  pitch  radii,  or  is  equal  to  one  half  the  sum  of 
their  teeth  divided  by  the  diametral  pitch. 

The  number  of  teeth  in  a  gear  may  be  found  by  multiplying 
together  the  pitch  diameter  and  the  diametral  pitch.  If  the  num- 
ber of  teeth  and  the  diametral  pitch  are  known,  the  pitch  diameter 
is  found  by  dividing  the  number  of  teeth  by  the  diametral  pitch 
and  if  the  number  of  teeth  and  the  pitch  diameter  are  known,  di- 
viding the  number  of  teeth  by  that  diameter  gives  the  diametral 
pitch. 

The  whole  diameter  in  any  case  equals  the  pitch  diameter  plus 
two  diametral  pitches,  or  if  the  number  of  teeth  and  diametral 
pitch  are  known  add  two  to  the  number  of  teeth  and  divide  by  the 
diametral  pitch.  In  cases  where  the  circular  pitch  is  given,  re- 
duce it  first  to  diametral  pitch  by  dividing  3.1416  by  it  and  apply 
the  above  rules. 

The  ratio  between  the  number  of  revolutions  that  one  gear 
makes  for  one  revolution  of  its  mating  gear  is  called  the  "velocity 
ratio."  This  ratio  equals  the  number  of  revolutions  of  one  gear 
in  a  given  time  divided  by  the  number  of  revolutions  of  the  other 
gear  in  the  same  time,  or  what  is  the  equivalent,  the  pitch  diame- 
ter of  one,  or  its  number  of  teeth,  divided  by  the  pitch  diameter 
or  number  of  teeth  of  the  other.  The  above  considers  the  gears 
as  round  and  turning  about  their  central  axes,  thus  giving  a 
constant  velocity  ratio.  This  is  the  condition  most  common  in 
practice. 

In  the  cases  of  lobed  and  elliptical  gearing,  the  velocity  ratio 
is  constantly  changing  and  for  any  part  of  a  revolution  must  be 
taken  in  terms  of  the  pitch  diameters,  acting  at  that  instant.  If 
the  ratios  of  complete  revolutions  are  considered,  they  may  be 
had  in  terms  of  the  revolutions  per  unit  of  time  or  the  number  of 
teeth. 


GEARlXr,.  467 

The  gears  in  common  use  may  be  divided  into  classes  as  fol- 
lows : 

First,  spur  gears ;  those  having  straight  tooth  elements  par- 
allel with  the  axis  and  used  for  connecting  parallel  shafts.  The 
teeth*  are  cut  on  parallel  cylinders. 

Second,  bevel  gears;  those  having  straight  tooth  elements 
which  meet  in  a  common  or  focal  point  and  are  used  for  connect- 
ing shafts  whose  prolonged  axes  intersect.  The  teeth  are  cut  on 
conical  surfaces. 

Third,  worm  gearing;  those  having  spiral  tooth  elements  and 
used  for  connecting  shafts  at  right  angles,  axes  not  intersecting. 
The  teeth  are  formed  on  cylindrical  surfaces. 

Fourth,  spiral  gears ;  often  called,  twisted,  screw,  or  helical 
gears ;  those  used  for  connecting  shafts  which  are  not  parallel 
and  do  not  intersect.  The  teeth  are  formed  on  cylindrical  sur- 
faces. 

As  it  is  of  very  great  importance  in  nearly  all  cases  to  main- 
tain a  constant  velocity  ratio  at  all  points  in  a  gear's  rotation,  care 
must  be  exercised  in  the  forming  of  the  teeth.  Many  forms 
of  tooth  outline  can  be  made  that  will  meet  this  requirement,  but 
for  reasons  of  a  practical  nature,  and  the  necessity  for  uniformity, 
but  two  systems  are  in  general  use — the  "involute"  and  the  "cy- 
cloidal"  systems.  Of  these  two  systems  the  "involute"  form  of 
tooth  is  the  more  used  and  considered  by  many  of  the  best  au- 
thorities on  gearing,  as  superior  to  the  "cycloidaF7  system.  In 
fact  the  general  adoption  of  this  system  has  been  strongly  urged 
and  from  the  point  of  uniformity  in  gearing  construction  would 
be  a  most  desirable  move. 

The  "involute"  tooth  has  a  single  curve  outline.  The  "invo- 
lute" curve  is  the  curve  generated  by  the  end  of  a  non-stretching 
band,  as  it  is  unwrapped  from  a  cylinder,  as  shown  in  Fig.  609. 
By  taking  the  points  a  and  b  comparatively  close  together  and 
setting  the  dividers  to  that  distance,  the  other  points,  c,  d,  e,  etc., 
may  be  stepped  off.  Through  each  point  draw  a  tangent  to  the 
circle  and  step  off  on  the  tangent  the  number  of  spaces  it  is  from 
the  origin  of  the  curve,  thus  locating  a  point  of  the  curve,  as 
shown  at  5.  The  curve  passing  through  a  series  of  points  thus 
located  is  the  "involute"  of  the  circle.  If  the  points  are  taken 
sufficiently  close  together  to  make  the  chord  and  its  arc  connect- 
ing them  practically  equal,  this  method  may  be  considered  exact. 

In  practice  a  curve  which  approximates  the  "involute"  curve 


468 


MODERN    MACHINE    SHOP    TOOLS. 


is  employed  and  the  circle  upon  which  it  is  laid  out  is  called  the 
base  circle.  This  circle  lies  inside  of  the  pitch  circle  an  amount 
differing  slightly  in  the  methods  practiced  by  the  leading  makers. 


FIG.  609. 


FIG.  6lO. 


Brown  &  Sharpe  make  the  diameter  of  the  base  circle  .968  of 
the  pitch  circle.  Their  graphical  method  of  making  the  single 
arc  approximation  for  gears  having  30  teeth  or  more,  is  shown 
in -Fig.  610.  Having  laid  down  the  addendum  and  pitch  circles, 


GEARING. 


469 


locate  the  pitch  point  B  and  take  the  other  pitch  points,  C,  D, 
etc.,  at  distances  from  E  =-  to  l/2  the  circular  pitch.  Describe 
the  semi-circle  B  O.  The  base  circle  passes  through  the  point 
A.  The  arc  B"  B'  described  about  A  as  a  center  gives  the  tooth 
outline  approximating  very  closely  to  the  true  "involute."  By 
stepping  around  the  base  circle  the  other  tooth  curves  may  be 
drawn  in. 

The  line  X  X  drawn  through  the  points  A  and  B  is  called  the 
line  of  action  and  is  in  the  Brown  &  Sharpe  system  14^  degrees 
from  the  normal  tangent  Y  Y. 

When  "involute"  gears  have  less  than  30  teeth,  the  single  arc 
approximation  cannot  be  used  inasmuch  as  the  space  left  is  too 


'M  LIME* 


FIG.  6ll. 

narrow  at  the  bottom,  causing  the  face  of  the  mating  gear  tooth 
to  interfere.  In  these  cases  the  arc  is  carried  from  the  addendum 
to  the  base  circle.  From  this  point  the  flank  is  drawn  for  a 
short  distance  parallel  with  a  radius  to  the  middle  of  the  tooth 
space  and  completed  with  a  short  arc  described  from  the  pitch 
center  of  the  adjacent  tooth  and  blended  into  a  fillet,  the  radius 
of  which  is  equal  to  1-6  the  width  of  the  space  at  the  addendum 
circle. 

By  some  authorities  the  single  arc  approximation  is  not 
recommended  for  tooth  outlines  of  gears  having  less  than  60 
teeth. 

The  tooth  of  the  "involute"  rack  has  straight  sides,  which 
are  at  right  angles  to  the  line  of  action,  as  shown  in  Fig.  611. 
When  the  rack  is  to  gear  with  pinions  having  fewer  than  30 


470 


MODERN    MACHINE    SHOP    TOOLS. 


teeth,  it  becomes  necessary  to  round  the  addendum  of  the  rack 
teeth  to  prevent  interference  with  the  flank  of  the  pinion  tooth. 

The  Grant  odontographic  method  of  laying  out  "involute" 
gear  teeth  to  approximate  arcs  is  given  in  the  following  table 
and  illustrated  in  Fig.  612. 

GRANT'S  INVOLUTE  ODONTOGRAPH. 


TEETH. 

Divide  by  the  Diametral  Pitch. 

Multiply  by  the  Circular  Pitch. 

Face  Radius. 

Flank  Radius. 

Face  Radius. 

Flank  Radius. 

10 

2.28 

.69 

•  73 

.22 

ii 

2.40 

•S3 

.76 

.27 

12 

2.51 

.96 

.80 

•31 

13 

2.62 

1.09 

.83 

•  34 

14 

2.72 

1.22 

.87 

•39 

15 

2.82 

•34 

.90 

43 

16 

2.92 

1.46 

•93 

•47 

17 

3-02 

1.58 

.96 

50 

18 

3.12 

.69 

•99 

•  54 

19 
20 

3.22 
3.32 

•79 

.89 

3 

•57 
.60 

21 

3.41 

.98 

.09 

•63 

22 

3-49 

2.06 

.11 

.66 

23 

3-57 

2-15 

•  T3 

.69 

24 

3-64 

2.24 

.16 

•7* 

25 

3-71 

2-33 

18 

.74 

26 

3-72 

2.42 

.20 

2? 

3-85 

2.50 

•23 

.80 

28 

3-92 

2  59 

•25 

.82 

29 

3-99 

2.67 

27 

.85 

30 

4.06 

2.76 

•29 

.88 

31 

4-13 

285 

.91 

32 

4.20 

2-93 

•34 

•93 

33 

4.27 

3.01 

•36 

.96 

34 

4.33 

3-°9 

.38 

.99 

35 

4-39 

•39 

i.  or 

36 

4-45 

3  23 

.41 

1.03 

37—40 

4  20 

i  34 

41—45 

4.63 

1.48 

46—51 

1.61 

52—60 

5-74 

1-83 

6  1  —  70 

6.52 

207 

71—90 

7.72 

2.46 

91  —  1  20 

9.78 

3.11 

121  —  8lO 

13.38 

4  26 

181—360 

21.62 

6.88 

Draw  the  rack  tooth  by  the  special  method. 

In  this  system  all  gears  up  to  37  teeth  have  tooth  outlines  to 
a  double  arc  approximation  and  above  that  number  a  single  arc 
outline.  These  determinations  are  based  on  a  15  degree  line  of 
action. 


GEARIXC,. 


471 


In  the  application  of  the  Grant  method,  Fig.  612,  the  pitch, 
addendum,  root,  working  depth  and  base  lines  are  laid  out.  The 
base  circle  is  taken  at  1-60  the  pitch  diameter  inside  of  the  pitch 
circle.  If  the  data  is  in  terms  of  the  diametral  pitch,  the  face 
and  flank  radii  are  taken  from  the  tabulated  columns  under  diam- 
etral pitch,  and  if  in  terms  of  the  circular  pitch  they  are  taken 
from  the  columns  under  circular  pitch.  These  values  are  divided 
or  multiplied,  as  indicated,  by  the  pitch.  The  pitch  points  are 
next  located,  and  with  the  dividers  set  to  the  face  radius,  the 
faces  are  drawn  in  from  the  pitch  point  to  the  addendum  with 
centers  in  the  base  circle ;  and  in  like  manner  with  the  flank  radius, 
the  flanks  are  drawn  in  from  the  pitch  point  to  the  base  line. 
From  the  base  line  to  the  working  depth  the  flank  is  a  radial  line 


FIG.  612. 

from  the  center  of  the  blank.  A  fillet  between  working  depth 
and  root  completes  the  tooth  outline.  The  rack  teeth  in  this 
system  have  flanks,  and  the  inner  half  of  the  faces,  at  15  degrees 
with  the  pitch  line.  The  outer  half  of  the  tooth  face  is  drawn 
from  a  point  in  the  pitch  line  with  a  radius  equal  to  2.10  inches 
divided  by  the  diametral  pitch  or  .67  inches  multiplied  by  the 
circular  pitch. 

Gears  having  the  "involute"  form  of  teeth  are  the  only  ones 
that  can  be  run  with  the  axes  at  varying  distances  and  still  trans- 
mit uniform  angular  velocity.  The  line  of  action  varies,  how- 
ever, as  the  axes  are  separated. 

In  the  "cycloidal"  system  of  gearing  the  tooth  outline  is  made 
up  of  a  double  curve,  the  face  being  an  "epicycloid"  and  the  flank 
a  "hypocycloid."  The  system  is  commonly  known  as  the  "epi- 
cycloidal"  system. 


4/2  MODERN    MACHINE    SHOP    TOOLS. 

An  "epicycloid"  is  the  path  of  a  point  in  the  generating  circle 
rolling  on  the  outside  of  another  circle,  which  in  gearing  problems 
is  the  pitch  circle.  A  "hypocycloid"  is  the  path  of  the  point  gen- 
erated when  the  circle  is*  rolled  on  the  inside  of  the  pitch  circle. 
These  curves  are  shown  in  Fig.  613. 

When  the  diameter  of  the  generating  circle  is  equal  to  the 
radius  of  the  pitch  circle  the  path  of  the  generating  point  is  a 
radial  line.  The  prevailing  practice  makes  the  flank  of  the  15 
tooth  gear  in  this  system  radial  which  for  an  interchangeable 
system  makes  the  diameter  of  the  generating  circles  equal  to  the 
pitch  radius  of  a  15  tooth  gear. 

in  the  Grant  system  a  gear  of  12  teeth  is  taken  as  the  basis, 


FIG.  613. 

which  gives  a  stronger  pinion  tooth  for  and  above  fifteen  teeth 
than  the  15-tooth  basis. 

The  rack  of  the  interchangeable  cycloidal  system  has  teeth 
of  double  curve  outline,  generated  by  rolling  the  generating  circle 
along  each  side  of  the  pitch  line,  as  shown  in  Fig.  614.  These 
curves  are  cycloids. 

Although  it  is  a  comparatively  simple  operation  to  lay  out 
the  "cycloidal"  form  of  tooth  by  means  of  the  rolling  generating 
circle,  numerous  approximate  methods  are  in  use.  Notably  the 
Grant  three-point  double  arc  approximation  and  the  Klein  method 
by  the  use  of  tabulated  co-ordinates,  which  latter  method  is  also 
applicable  to  the  "involute"  tooth  outlines. 


GEARING. 


473 


In  the  "cycloidal"  form  of  tooth  the  line  of  action  is  perpen- 
dicular to  the  line  of  centers  when  the  point  of  contact  crosses 
that  line.  For  all  other  points  of  contact  the  line  of  action  is  at 
an  angle  with  the  line  of  centers,  being  a  maximum  at  the  points 
where  the  teeth  make  and  break  contact.  In  general  practice  the 
line  of  action  in  cycloidal  gears  varies  from  zero  degrees  at  the 
line  of  centers  to  about  30  degrees  each  side  of  this  line. 

"Cycloidal"  'teeth  are  conjugate  only  when  the  centers  of  the 
gears  are  properly  pitched  and  will  not  admit  of  as  wide  varia- 
tions in  form  and  adjustment  as  will  the  "involute"  teeth.  As 
the  form  of  a  tooth  in  either  system  changes  for  every  number 
of  teeth,  a  cutter  can  be  of  correct  outline  for  but  one  number  of 
teeth.  For  ordinary  requirements,  however,  8  cutters  for  the 


FIG.  614. 


FIG.  615. 


''involute"  and  24  for  the  "cycloidal"  cut  all  numbers  of  teeth, 
in  any  one  pitch  from  12  to  a  rack. 

The  annular  or  internal  gear  is  a  spur  gear  in  which  the  teeth 
are  on  the  inside  of  the  rim.  In  the  internal  gear,  an  example  of 
which  is  shown  in  Fig.  615,  the  teeth  correspond  with  the  spaces 
of  an  external  spur  gear.  Annular  gears  may  have  either  the 
"involute"  or  "cycloidal"  form  of  teeth.  They  come  under  the 
same  general  rules  as  for  external  spur  gearing.  The  limitations 
are,  however,  more  closely  drawn. 

Bevel  gears  are  used  to  communicate  motion  from  one  shaft 
to  another  when  the  axes  of  the  shafts  intersect.  In  most  cases 
the  axes  are  at  right  angles  with  each  other.  They  may,  however, 
be  at  any  angle,  their  limits  being  the  external  and  internal  spur 
gears,  at  which  points  the  axes  become  parallel. 


474 


MODERN    MACHINE    SHOP    TOOLS. 


As  in  spur  gearing,  where  we  assumed  two  cylinders  as  rolling 
together,  we  may  in  bevel  gearing  assume  two  cones  or  portions 
of  cones  as  rolling  together.  If  they  roll  without  slipping,  the 
angular  velocity  is  the  same  for  all  points  and  the  velocity  ratio 
is  the  same  at  any  point  between  the  base  and  the  apex.  If  now 
we  assume  the  surfaces  of  these  cones  as  pitch  surfaces,  and  pro- 
duce teeth  upon  them,  all  lines  of  which  terminate  in  the  apex  or 
focal  point,  we  have  a  pair  of  bevel  gears  which  will  roll  to- 


pic. 616. 


gether  without  slipping  and  will,  if  the  teeth  are  of  correct  form, 
maintain  the  same  velocity  ratio  as  will  the  pitch  cones. 

In  bevel  gears  the  relations  between  pitch  diameter,  pitch 
and  numbers  of  teeth  and  velocities  are  the  same  as  for  spur 
gearing,  thus  making  calculations  pertaining  to  these  points,  the 
same  as  given  for  spur  gears. 

In  obtaining  the  data  for  bevel  gears  it  is  customary  to  make 
a  sectional  drawing  of  one-half  of  each  gear.  In  Fig.  616  is 
shown  the  usual  method  of  laying  out.  The  two  axis  or  shaft 
centers  O  G  and  O  H  and  the  maximum  pitch  diameters  L  M 
and  M  F  are  laid  out,  the  latter  of  lengths  proportionate  to  the 


GEARING. 


475 


required  velocity  ratio.  The  pitch  cone  lines  L  O,  M  O  and  F  O 
and  the  back  cone  radii  M  G  and  M  H  are  drawn.  The  calcula- 
tions for  the  teeth  are  based  on  the  largest  pitch  diameter.  Look- 
ing at  the  gears  from  the  direction  indicated  by  the  arrow  the 
ends  of  the  teeth  appear  as  would  the  ends  of  teeth  of  spur  gears, 
having  pitch  radii  equal  to  the  back  cone  radii  M  G  and  M  H. 
The  outline  of  the  tooth  is  laid  out,  as  shown,  in  the  same  man- 
ner as  for  spur  gears. 

The  whole  diameters  X  X  and  the  pitch,  root  and  top  angles 
are  usually  measured  from  carefully  made  drawings. 

The  teeth  of  bevel  gears  may  be  of  the  "involute"  "cycloidal," 
of  "octoidal"  forms  and  can  be  correctly  formed  only  by  a  plan- 
ing process.  They  may  be  cut  to  approximate  form  by  a  rotat- 


FIG.  617. 


FIG.  618. 


ing  cutter,  a  method  very  largely  employed  especially  on  small 
gears. 

Bevel  gears  of  the  same  size  connecting  shafts  at  right  angles 
are  termed  miter  gears. 

The  efficiency  of  correctly  cut  spur  and  bevel  gears  is  high, 
ranging  from  90  to  99  per  cent,  "depending  upon  velocity  and  per- 
fectness  of  their  application. 

Skew  bevel  gears  are  those  used  in  connecting  shafts  which 
are  not  parallel  and  do  not  intersect.  They,  are  but  little  used. 

The  worm  gear  and  worm,  an  example  of  which  is  shown 
in  Fig.  617,  is  used  for  transmitting  motion  from  one  shaft  to 
another  at  right  angles  to  it,  axes  not  intersecting.  The  worm 
and  gear  is  a  limiting  case  in  spiral  gearing,  the  worm  corres- 
ponding to  a  spiral  gear  having  but  one  tooth. 


MODERN    MACHINE    SHOP    TOOLS. 


The  section  of  the  worm  as  shown  at  S,  Fig.  618,  is  of  the 
same  outline  as  a  rack  of  corresponding  pitch  and  may  be  of 
either  the  ''involute"  or  "cycloidal"  form.  The  "involute'7  is  the 
form  usually  employed,  as  the  straight  sides  of  its  teeth  are 
much  easier  to  produce  on  the  hobbing  cutter,  Fig.  474,  which 
is  used  in  cutting  the  worm  gear,  than  the  "cycloidal"  form. 

As  worms  are  usually  cut  in  the  lathe  using  the  regular 
change  gears,  their  pitch  is  expressed  in  terms  of  circular  pitch 
rather  than  diametral.  This  pitch  is  usually  called  the  lead  of  the 
worm  and  is  the  amount  the  thread  advances  at  each  revolution. 
The  spaces  between  the  teeth  of  the  worm  from  which  the  hob 
is  to  be  made  are  cut  without  clearance  and  the  whole  diameter 


-THROAT  DIAM. 

OOT  DIAW. 


FIG.   619. 

is  made  greater  than  the  diameter  of  the  worm  by  twice  the 
amount  of  the  root  clearance  necessary. 

In  Fig.  619  is  shown  an  end  section  of  worm  and  worm  gear, 
The  whole  diameter,  throat  diameter,  pitch  diameter,  and  root 
diameter  are  indicated  in  the  figure.  These  dimensions  are  found 
by  the  same  rules  as  for  spur  gearing. 

The  diameter  of  the  worm  is  usually  taken  at  from  four  to 
five  times  the  pitch,  but  is  not  limited  in  diameter,  thus  making 
possible  considerable  variation  in  the  pitch  centers.  As  with 
"involute"  gears,  the  velocity  ratio  remains  constant  when  the 
axes  are  separated.  This  is  frequently  made  use  of  in  the  case 
of  low  numbered  worm  gears  to  avoid  tooth  interference.  With 
the  usual  worm  thread,  having  its  sides  at  14^  degrees  with  the 
axis,  interference  begins  at  30  teeth  when  the  pitch  circles  touch. 
By  slightly  rounding  the  ends  of  the  thread  faces,  as  with  racks 


GEARING. 


477 


gearing  with  low  numbered  pinions,  this  interference  can  be 
overcome  for  worm  gears  having  a  number  of  teeth  under  30. 
Separating  the  pitch  lines  of  correctly  formed  worms  and  worm 
gears,  although  overcoming  interference,  produces  excessive  back 
lash.  The  same  results  without  the  back  lash  may  be  obtained 
by  enlarging  the  outside  diameter  of  the  worm  gear,  thus  giving 
the  tooth  a  short  flank  and  bringing  the  action  largely  upon  the 
faces  of  the  teeth.  These  are  extreme  cases  and  should,  if  pos- 
sible, be  avoided.  When  the  required  velocity  ratio  necessitates 
a  gear  of  fewer  than  30  teeth,  it  is  preferable,  if  possible,  to  double 
the  number  of  teeth  and  use  a  double  thread  worm. 

Worm  gearing  is  largely  used  in  places  where  a  great  velocity 
ratio  is  necessary  with  as  few  gears  as  possible.  It  is  a  locking 
mechanism  in  which  the  worm  must  always  be  the  driver.  This 
feature  is  made  use  of  very  largely  in  the  application  of  this  class 
of  gearing  to  elevators  and  dividing  mechanisms. 

The  tooth  action  is  purely  a  sliding  one  and  consequently  this 
class  of  gearing  is  not  well  adapted  to  the  transmission  of  heavy 
powers  as  its  efficiency  is  necessarily  low,  from  50  to  75  per  cent, 
and  the  wear  is  in  such  cases  usually  excessive. 

When  used  for  heavy  service  the  concave  form  of  tooth  shown 
at  A  in  Fig.  620  is  best  suited,  due  to  its  greater  tooth  surface. 


MODERN    MACHINE    SHOP    TOOLS. 

The  form  shown  at  C  is  largely  used  on  dividing  mechanisms 
where  the  strains  are  not  great,  and  the  form  shown  gives  better 
protection  to  the  teeth  against  injury.  The  form  shown  at  B 
has  but  one  advantage  and  that  is  the  possibility  of  its  being  cut 
in  a  milling  machine  without  the  use  of  a  hob.  The  teeth  are  cut 
with  a  spur  gear  cutter  at  the  angle  corresponding  with  the  angle 
of  the  helix  of  the  worm.  As  this  gives  a  very  imperfect  contact 
between  the  teeth  of  gear  and  worm,  it  is  suited  only  to  the  trans- 
mitting of  very  light  loads.  When  the  teeth  are  so  formed  it  is 
possible  to  vary  somewhat  the  angle  of  the  axes  from  a  right 
angle,  as  for  example,  if  the  gear  shown  at  B  was  a  spur  gear, 
the  worm  would  mesh  with  it  by  inclining  its  axis  from  its  normal 


position  an  amount  equal  to  the  angle  of  its  helix.  This  pro- 
duces an  objectionable  pressure  in  the  direction  of  the  gear's  axis. 

The  distinction  between  worm  and  spiral  gearing  is  not  closely 
drawn.  As  the  worm  and  worm  gear  approach  each  other  in  dia- 
meter, and  the  gear  is  given  a  low  number  of  teeth  with  multiple 
threads  on  the  worm,  the  problem  blends  from  one  of  worm  into 
one  of  spiral  gearing. 

Take  a  number  of  thin  spur  gears  that  have  been  cut  together, 
shift  them  slightly  about  their  axes  so  that  the  teeth  do  not  line, 
a?  shown  at  A,  Fig.  621,  and  we  have  what  is  termed  a  "stepped" 
gear.  Such  a  gear  when  running  with  a  similar  stepped  gear  will 
have  a  number  of  teeth  constantly  in  contact,  with  practically  one 
pair  always  passing  the  line  of  centers,  thus  producing  a  smoother 
motion  than  can  be  obtained  with  the  common  spur  gears.  If  we 
•consider  these  elementary  gears  as  being  extremely  thin,  the  teeth 


GEARING. 


479 


will  blend  into  each  other,  forming  what  is  known  as  the  twisted 
gear,  the  outline  of  the  teeth  being  of  any  desired  form.  When 
the  teeth  have  a  uniform  spiral  as  shown  at  B,  Fig.  621,  the  gear 
is  called  a  screwr  or  spiral  gear. 

When  the  teeth  of  twisted  gears  are  other  than  true  spirals, 
they  must  work  together  the  same  as  spur  gears  on  parallel  axes, 
the  pitch  surfaces  rolling  upon  each  other.  With  screw  gearing 
the  axes  may  be  at  any  angle  with  each  other,  and  for  all  angles 
there  will  be  sliding  contact  between  the  teeth  along  the  pitch 


FIG.  622. 


FIG.  623. 


surfaces,  it  being  greatest  when  the  axes  are  at  90  degrees  with 
each  other. 

In  practice  the  teeth  of  twisted  gears  are  formed  to  a  true 
spiral,  all  such  gears  being  technically  known  as  spiral  gears. 

The  pitch  of  a  spiral  is  the  distance  it  advances  in  one  revolu- 
tion and  corresponds  to  the  pitch  or  lead  of  a  screw  thread.  It 
is  a  true  helical  curve,  which,  when  developed  on  a  plane,  becomes 
a  straight  line,  as  shown  in  Fig.  622  at  A  C  D  B,  where  E  F  = 
the  pitch  and  F  B  the  circumference  of  the  cylinder  on  which  the 
spiral  is  wound,  a  =  the  angle  of  the  spiral  with  the  axis  and  is 


480  MODERN'    MACHINE    SHOP    TOOLS. 

termed  the  spiral  angle.  The  spiral  angle  for  equal  pitches  varies 
•  with  the  diameter  of  the  cylinder  on  which  the  curve  is  drawn. 
The  smaller  the  cylinder  the  less  the  angle.  With  a  cylinder  of  in- 
finite diameter  the  angle  becomes  90  degrees,  and  the  curve  a 
straight  line,  which  gives  in  practice  the  rack  tooth. 

The  pitch  surface  of  a  spiral  gear  is  cylindrical,  and  all  pitch 
calculations  are  based  on  this  surface. 

The  normal  helix  is  a  spiral  curve  on  the  pitch  surface  cross- 
ing the  teeth  at  right  angles.  Upon  this  curve  the  normal  circular 
pitch  B,  Fig.  623,  is  measured.  A  is  the  circular  pitch.  The  ad- 
dendum and  tooth  outline  are  determined  from  the  normal  pitch 
B,  not  from  the  circular  pitch  A,  as  in  spur  gearing,  as  in  that 
case  a  cutter  of  thickness  equal  to  one-half  A  at  pitch  line  would 
remove  too  much  stock,  making  the  tooth  too  thin.  By  using  the 
normal  pitch,  however,  we  are  enabled  ordinarily  to  cat  spiral 
gears  with  regular  gear  cutters. 

The  teeth  of  spiral  gears  may  be  either  right  or  left  hand 
spirals,  the  distinction  between  right  and  left  being  the  same  as 
for  screw  threads.  When  the  axes  are  parallel,  as  at  C,  Fig.  621, 
one  gear  must  have  right  and  the  other  left  hand  spirals,  and 
the  spiral  angles  must  be  equal  in  each  gear.  This  angle  is  usu- 
ally taken  small,  seldom  exceeding  20  degrees.  If  too  great  an 
angle  is  taken,  the  end  thrust  on  the  bearings,  due  to  the  tendency 
of  the  teeth  to  slip  on  each  other  along  the  pitch  line,  will  be  ex- 
cessive. The  angle  should  be  great  enough  to  insure  at  least  two 
pairs  of  teeth  having  contact  points  constantly  passing  the  line  of 
centers.  The  width  of  faces  will  determine  largely  the  angle  to 
use  in  any  case,  wider  faces  and  smaller  angles  going  together. 

Since  in  spiral  gears  on  parallel  axes  the  spiral  angles  must 
be  equal,  the  pitch  of  spiral  will  be  equal  in  both  gears  only  when 
they  are  of  the  same  diameter.  If,  for  example,  one  gear  has  three 
times  the  pitch  diameter  of  the  other,  in  order  to  have  the  same 
spiral  angle  its  spiral  pitch  must  be  three  times  as  great. 

With  the  axes  at  right  angles  both  gears  will  have  either  right 
or  left  hand  spirals. 

Consider  a  pair  of  spiral  gears  on  parallel  axes  A  and  B,  at  C, 
Fig.  621,  with  spiral  angles  of  45  degrees.  Gear  A  has  a  right 
hand  spiral  and  B  a  left  hand.  Gradually  swing  the  axis  of  A 
away  from  that  of  B.  Assuming  that  the  spiral  angle  of  A 
changes, it  will  gradually  decrease  until  it  becomes  zero  degrees  and 
we  have  a  spur  gear  when  the  axis  of  A  is  at  45  degrees  from  the 


GEARING.  481 

axis  of  B.  Continuing  to  swing  A,  the  spiral  angle  changes  from 
right  to  left  hand,  and  at  90  degrees  it  becomes  the  same  as  B.  If 
any  other  spiral  angle,  as  20  degrees,  had  been  taken,  A  would  have 
become  a  spur  gear  when  its  axis  had  passed  through  an  angle 
equal  to  the  spiral  angle  or  20  degrees,  and  beyond  that  position 
the  spiral  would  be  left  handed,  increasing  to  70  degrees  at  the 
9<>degree  axis  position.  From  this  the  following  rules  are  de- 
duced:  First — When  the  gears  both  have  right  or  left  hand 
spirals  the  sum  of  the  spiral  angles  equals  the  angle  between 
axes;  second — When  the  gears  are  right  and  left  handed,  the 
difference  of  the  spiral  angles  equals  the  angle  between  axes. 

The  velocity  ratio  of  spiral  gears  cannot  be  determined  by 
direct  comparison  of  pitch  diameters,  as  in  spur  gearing,  but  must 
be  found  from  the  angles  of  the  spiral  in  each  gear.  Thus  if  the 
spiral  angles  of  two  gears  are  the  same,  the  velocity  ratio  will  be 
inversely  as  the  pitch  diameters,  but  if  the  spiral  angles  are  not 
equal,  the  number  of  teeth  per  inch  of  pitch  diameter  will  vary 
and  the  above  ratio  will  not  hold. 

This  is  well  illustrated  in  a  worm  and  worm  wheel,  where,  if 
the  worm  has  a  single  thread,  it  is  really  a  spiral  gear  having  a 
single  tooth,  and  the  velocity  ratio  will  be  the  number  of  teeth 
in* the  gear.  If  the  worm  has  two,  three  or  more  teeth,  the  spiral 
angle  will  be  different  in  each  case  and  the  velocity  ratio  equal 
to  the  number  of  teeth  in  the  gear  divided  by  the  number  of  teeth 
in  the  worm.  Increasing  or  decreasing  the  pitch  diameter  of  the 
worm  will  change  the  spiral  angle  of  the  teeth  in  gear  and  worm, 
but  will  not  affect  the  velocity  ratio.  In  any  case  the  velocity  ratio 
will  depend  upon  the  number  of  teeth  and  their  spiral  angle,  as  ex- 
pressed in  the  following  proportion :  v,  the  velocity  of  the  small 
gear,  is  to  V,  the  velocity  of  the  large  gear,  as  D,  the  pitch  dia- 
meter of  the  larger,  times  the  cosine  of  its  spiral  angle  is  to  d,  the 
pitch  diameter  of  the  smaller,  times  the  cosine  of  its  spiral  angle. 

With  the  axes  at  any  angle  the  teeth  slide  upon  each  other, 
this  action  being  the  greatest  when  the  axes  are  at  right  angles 
with  each  other.  As  this  sliding  contact  produces  friction  between 
the  teeth  and  excessive  end  thrust  along  the  axes,  spiral  gears 
with  axes  other  than  parallel  or  nearly  so  are  not  suitable  for 
transmitting  heavy  powers  at  high  velocities,  as  the  wear  is  ex- 
cessive and  the  frictional  losses  make  the  efficiency  low.  When 
the  axes  are  at  right  angles  as  in  the  spiral  worm  gear  and  worm, 
the  conditions  are  the  most  unfavorable  for  the  economic  trans- 


482  MODERN    MACHINE    SHOP    TOOLS. 

mission  of  power,  the  efficiency  frequently  falling  below  50  per 
cent. 

In  all  spiral  gearing  an  end  thrust  along  the  axes  is  pro- 
duced by  the  oblique  action  of  the  teeth.  This  effect  may  be 
neutralized  by  placing  gears  of  opposite  spirals  on  the  same  shaft, 
as  shown  in  Fig.  624  at  A. 

Before  laying  out  spiral  gearing  the  designer  will  do  well  to 
consult  the  shop  facilities  for  cutting  them,  since  their  special 
character  will  usually  enable  him  to  adapt  them  to  the  cutters  in 
stock,  and  only  in  unusual  cases  will  he  find  it  necessary  to  use  any 
other  than  standard  cutters. 

It  will  usually  be  found  satisfactory  to  determine  tooth  and 


FIG.  624. 

rim  proportions  from  the  rules  for  spur  gearing.  If  the  gears' 
are  of  large  diameter,  the  arms  must  be  made  sufficiently  heavy 
to  resist  the  pressure  in  the  direction  of  the  axis  due  to  the  oblique 
action  at  the  teeth.  As  the  pressure  between  teeth  is  confined  to  a 
very  small  surface,  the  strain  on  the  tooth  is  more  severe  than  in 
the  spur  gearing,  and  the  consequent  wear  due  to  friction  much 
greater. 

In*  considering  spirai  gearing  the  following  constitutes  the 
most  important  data :  First — The  position  of  the  axes,  whether 
parallel  or  at  an  angle  with  each  other ;  second — the  distance  be- 
tween centers,  whether  at  a  fixed  distance,  or  allowing  a  small 


GEARING.  483 

variation  in  the  distance ;  third — the  velocity  ratio ;  and  fourth — 
the  power  to  be  transmitted. 

When  the  distance  between  centers  is  fixed,  it  will  often  be 
found  difficult  to  obtain  correct  velocity  ratios,  as  the  normal 
circular  pitch  will  usually  give  a  fractional  diametral  pitch  which 
would,  unless  approximately  close  to  some  standard  pitch,  require 
a  special  cutter.  When  the  distance  between  centers  can  be  varied, 
as  is  usually  the  case,  the  proper  numbers  of  teeth,  with  their 
spiral  angles,  to  give  the  desired  velocity  ratio,  may  be  selected, 
and  the  correct  normal  circular  pitch  to  suit  a  standard  cutter  as- 
sumed. The  circular  pitch  then  equals  the  normal  circular  pitch 
divided  by  the  cosine  of  the  spiral  angle.  The  circular  pitch  times 
the  number  of  teeth  equals  the  pitch  circumference  of  the  blank 
from  which  the  pitch  diameter  of  the  blank  may  be  found.  The 
whole  diameter  will  equal,  as  in  spur  gearing,  the  pitch  diameter 
plus  two  times  the  addendum.  The  addendum  equals 

I  inch 


Diametral  pitch 

The  involute  form  of  tooth  is  the  one  generally  used. 

In  the  pair  of  gears  shown  at  C  in  Fig.  621,  the  distance  be- 
tween centers  is  fixed  at  2  inches  and  the  velocity  ratio  is  one; 
the  pitch  diameters  are  2  inches,  and  since  the  axes  are  paral- 
lel the  spiral  angles  and  numbers  of  teeth  must  be  equal  in  each 
gear.  In  the  gear  shown  the  spiral  angle  is  45  degrees  and  the 
diametral  pitch  10,  giving  20  teeth  in  each  gear.  Pitch  circum- 

6.2832  inches 

ference  =  2  it  —  6.2832  inches ;  circular  pitch  = 

20 
=  .3141  inch;   normal  circular  pitch  =  .3141  inch  cos  45  degrees 

3.1416 
=  .2213  ;  normal  diametral  pitch  =  =  14.15  =  14  approx- 

.2213 
imately. 

2 

Whole  diameter  =  2  inches  -| =  2  1/7  inches. 

14 

By  increasing  the  pitch  diameter  slightly  a  14-?.  cutter  would 
be  correct,  but  since  from  data  that  is  not  permissible  it  will  be 


484  MODERN    MACHINE    SHOP    TOOLS. 

necessary  to  use  a  cutter  having  the  fractional  pitch  14.15,  or 
cut  the  teeth  slightly  shallower  than  exactness  would  demand, 
using  a  14-?.  cutter.  The  latter  method  would  ordinarily  be 
followed. 

Having  determined  the  pitch  of  the  cutter,  the  next  step  is  to 
find  the  shape  of  cutter  to  use,  as  indicated  by  the  numbers.  This 
may  be  obtained  from  the  expression  used  by  the  Brown  & 
Sharpe  Manufacturing  Company,  where  T,  the  number  of  teeth 
stamped  on  cutter,  =  N  ,  the  number  of  teeth  in  gear,  *f-  by  the 

20 
cosine2  of  the  spiral  angle.     In  the  present  case  T  =  —  =  4°> 

•5 
which  requires  cutter  No.  3. 

The  pitch  of  the  spiral  must  be  next  determined.  In  any  case  it 
will  equal,  from  Fig.  622,  the  pitch  circumference  -r-  by  the 

6.2832  inches 
tangent  of  the  spiral  angle,  =  in  above  case  ----  =  6.28 

i 
inches. 

PROBLEM   2.  -  AXES  PARALLEL,  VELOCITY  RATIO   lj£. 

In  Fig.  624  at  B  is  shown  a  pair  of  spiral  gears  on  parallel 
axes,  in  which  the  velocity  ratio  is  one  and  one-half.  From  con- 
siderations for  strength  these  gears  should  have  teeth  cut  with  a 
lo-P.  cutter.  Assume  : 

Spiral  angle,  25  degrees. 
Number  of  teeth  in  pinion,  24. 
Number  of  teeth  in  gear,  36. 
Normal  circular  pitch,  .314. 
Normal  diametral  pitch,  .10. 


Circular  pitch  =  —  —  =  .335. 

cos  25  degrees 

For  the  Pinion. 
Pitch  circumference  =  .335  X  24  =  8.04. 

8.04 

Pitch   diameter  =  =  2.56  inches. 

3.1416 


GEARING.  485 


2  inches 
Whole  diameter  =  2.56  -(-  -  -  =  2.76  inches 


10 


24 

Number  of   cutter  = =   29,   giving   cutter 

cos2  25  degrees 
No.  4. 

8.04 

Pitch  of  spiral  = =  17.25  inches. 

tan  25  degrees 

For  the  Gear. 
Pitch  circumference  =  .335  inch  X  36  =  12.06  inches. 

12.06  inches 

Pitch   diameter  =  =  3.83  inches. 

3.1416 

2 

Whole  diameter  =  3.83  inches  +  -      =  4-O3  inches. 

10 

36 
Number   of   cutter  =  -  -  ==  44,    giving    cutter 

cos2  25  degrees 
No.  3. 

12.06 

Pitch  of  spiral  = -  25.88  inches. 

tan  25  degrees 

The  spiral  of  one  should  be  right-handed,  of  the  other  left- 
handed.  The  distance  between  centers  equals  one-half  the  sum 
of  the  pitch  diameter,  •==  3.185.  This  distance  may  be  changed 
by  increasing  or  decreasing  the  number  of  teeth ;  of  course  the 
change  in  the  number  must  be  such  as  not  to  affect  the  velocity 
ratio. 

PROBLEM    3. AXES    AT    RIGHT    ANGLES. 

Consider  next  the  case  of  spiral  gears  with  axes  at  right  angles, 
as  shown  in  Fig.  623.  In  this  case  the  velocity  ratio  will  be  pro- 


486  MODERN    MACHINE    SHOP    TOOLS. 

portional  to  the  pitch  diameters  only  when  the  spiral  angle  is  45; 
degrees.    In  both  gears  assume  the  following  case  : 

Velocity  ratio,  i  to  2^. 

Normal  diametral  pitch,  No.  8. 

Number  of  teeth  in  gear,  30. 

Number  of  teeth  in  pinion,  12. 

Spiral  angle  of  teeth  in  gear,  30  degrees. 

To  determine  the  following: 

For  the  Gear. 
Normal  circular  pitch  =  .393  inch. 

.393  inch 

Circular  pitch  =  —  =  .4385  inch. 

cos  30  degrees 

Pitch  circumference  =  .4385  X  30=  13.155. 

I3-I55 

Pitch  diameter  =  -  =  4.  18  inches. 
3.1416 

2  inches 

Whole  diameter  =  4.18  inches  +  -          —  =  4.43  inches. 

8 

30 

Number    of   cutter  —  -         -  =  40,    giving    cutter 
cos2  30  degrees 

No.  3. 

13.155  inches 

Pitch  of  spiral  =  -  =  22.8  inches. 

tan  30  degrees 

For  the  Pinion. 

Spiral  angle  of  teeth  in  pinion  =  90  degrees  —  30  degrees  =• 
60  degrees. 

Normal  circular  pitch  =  .393  inch. 


•393 

Circular  pitch  =  —  —  =  .786  inch. 

cos  60  degrees 


GEARING.  487 

Pitch  circumference  =  .786  inch  X  12  =  9.432  inches. 

9432 

Pitch  diameter  =  —  =  3  inches 

3.1416 

2  inches 

\\  iioie  diameter  —  3  inches  -| =  3.25  inches. 

8 

12 

Number   of   cutter  = =  30,    giving   cutter 

cos2  60  degrees 
No.  4. 

9-432 

Pitch  of  spiral  =  —  =  5.44  inches, 

tan  60  degrees 

4.18  +  3 

Distance  between  centers  =  =  3.59  inches. 

2 

On  account  of  the  great  obliquity  of  the  teeth  the  pinion  should 
be  the  driver,  and  in  general  the  gear  having  the  larger  spiral 
angle  should  be  the  driver. 

PROBLEM    4. AXES   OBLIQUE. 

Taking  up  next  the  case  where  the  axes  are  neither  parallel 
nor  at  right  angles. 

Assume  the  following  data : 

Velocity  ratio,  i.  to  2*4 • 
Normal  diametral  pitch,  10. 
Number  of  teeth  in  pinion,  16. 
Number  of  teeth  in  gear,  36. 
Angle  between  axes,  50  degrees. 

If  the  end  thrust  is  to  be  equally  divided  between  the  bear- 
ings of  the  two  gears,  then  the  spiral  angle  of  each  gear  should 
be  one-half  the  angle  between  axes,  or  for  the  above  problem 
25  degrees ;  and  both  gears  will  have  right  or  left-hand  spirals. 
If,  however,  the  minimum  amount  of  sliding  between  teeth  is 


488 


MODERN    MACHINE    SHOP    TOOLS. 


desired,  then  the  graphical  method  given  by  MacCord  may  be 
used.  It  may  be  stated  thus :  The  angle  between  the  axis  of 
each  gear  and  the  diagonal  of  the  parallelogram  having  for  ad- 
jacent sides  lines  in  the  axis  and  corresponding  in  length  to 
the  velocity  of  each  gear.  Fig.  625  gives  the  approximate  spkal 


FIG.  625. 

angles.     In  the  present  case  the  resulting  angles  are  15  degrees 
for  the  pinion  and  35  degrees  for  the  gear. 

The  Brown  &  Sharpe  Company's  practice  is  to  take  a  mean 
between  the  angles  given  by  these  two  methods,  which  gives  for 
the  above  20  degrees  for  the  pinion  and  30  degrees  for  the  gear. 
On  this  basis  the  determinations  are  as  follows : 

For  the  Gear. 

Spiral  angle  =  30  degrees. 
Normal  circular  pitch  =  .314  inch. 

.314  inch 

Circular  pitch  =  —  =  .362  inch. 

cos  30  degrees 

Pitch  circumference  =  .362  inch  X  36=13.032  inches. 

13.032  inches 

Pitch  diameter  = =  4.18  inches. 

3.1416 


GEARING.  489 

2  inches 

Whole  diameter  =  4.18  inches  +  -  =  4.38  inches. 

10 

36 

Number   of   cutter  =  =  48,   giving   cutter 

cos2  30  degrees 

No.  3. 

13.032  inches 

Pitch  of  spiral  =  =  22.58  inches, 

tan  30  degrees 

For  the  Pinion. 

Spiral  angle  =  20  degrees. 
Normal  circular  pitch  =  .314  inch. 

.3 14  inch 

Circular  pitch  =  —  =  .334  inch, 

cos  20  degrees 

Pitch  circumference  =  .334  inch  X  16  =  5-344  inches. 

5.344  inches 

Pitch  diameter  = : =  1.7  inches. 

3.1416 

2  inches 

Whole  diameter  =  1.7  inches  -j =  1.9  inches. 

10 

16 

Number    of    cutter  =  =14,    giving   cutter 

cos2  20  degrees 

No.  7. 

5.344  inches 

Pitch  of  spiral  =  -  =  14.6  inches, 

tan  20  degrees 

Distance  between  centers  =  2.94  inches. 

A  pair  of  gears  cut  according  to  this  data  is  shown  in  Fig. 
624  at  C. 


CHAPTER   XXXII. 

BELTING    AND    TRANSMISSION    MACHINERY. 

The  transmission  of  power  by  belting  is  a  subject  of  great 
importance  and  one  that  should  receive  more  thought  and  study 
on  the  part  of  the  machinist.  A  better  knowledge  of  the  charac- 
teristics of  belting  and  the  problems  of  belt  gearing  increases 
materially  the  respect  of  the  average  mechanic  for  a  piece  of  good 
leather. 

A  belt  is  a  flexible  band  passing  over  two  or  more  pulleys  for 
the  purpose  of  transmitting  motion  from  the  one  to  the  other. 
As  its  drive  depends  on  its  frictional  resistance  to  slipping  and  as 
it  is  of  a  more  or  less  elastic  nature,  it  cannot  be  depended  upon  for 
the  transmission  of  exact  velocity  ratios. 

There  are  two  general  classes  of  belting,  flat  and  round,  the 
former  being  used  on  flat  or  crowned  pulleys,  the  latter  on  grooved 
or  sheave  pulleys.  The  materials  used  in  the  manufacture  of 
belting  are  leather  and  cotton  for  flat  belts,  and  leather,  cotton, 
and  manila  for  the  round  belts.  Rubber  is  extensively  used  on 
cotton  belts  for  increasing  the  driving  power  and  rendering  them 
weather  proof.  Of  the  above  materials  leather  is  the  most  im- 
portant and  the  one  most  used  in  manufacturing  works. 

Leather  belting  is  made  in  various  grades,  and  there  is  prob- 
ably no  other  material,  lubricating  oils  excepted,  with  which  the 
manufacturer  comes  in  contact  that  requires  better  judgment  in 
its  selection.  The  careful  selecting  of  the  hides,  the  proper  tan- 
ning and  currying,  and  above  all  the  part  of  the  hide  used  in  the 
belt,  together  with  care  used  in  its  manufacture,  are  the  important 
points  in  the  making  of  a  good  piece  of  leather  belting. 

In  Fig.  626  is  shown  a  cut  illustrating  the  character  of  the 
leather. used  for  belting.  That  portion  included  in  the  dotted  lines 
I  M  P  L  is  used  for  the  various  grades  of  belt,  and  is  termed 
a  "butt."  That  portion  of  the  hide  outside  of  the  "butt"  is  soft  and 
flabby,  and  although  frequently  used  in  cheap  belts,  is  totally  unfit 
for  the  purpose.  The  portion  E  F  G  H  is  known  as  the  center 
stock  and  is  that  part  used  in  the  making  of  the  better  belts.  Of 
the  center  stock  the  portion  A  B  C  D  is  the  best,  as  it  is  the 
strongest  and  most  uniform  part  of  the  hide.  The  portion 


BELTING  AND  TRANSMISSION    MACHINERY. 


491 


J  M  P  K  is  known  as  shoulder  stock  and  used  for  the  lower 
grades  of  belting.  What  is  known  as  strictly  short  lap,  center 
stock  belt,  must  be  cut  from  the  portion  A  B  C  D.  As  there  is  so 
small  a  piece  of  this  grade  of  leather  in  each  hide  it  goes  without 
question  that  much  of  the  so-called  center  stock  comes  from  the 
parts  E  F  B  A  and  D  C  G  H,  with  tendency  to  run  into 
the  portion  J  M  P  K.  The  shoulder  stock  is  tough  and  heavy, 
but  stretches  in  an  irregular  manner  and  should  not  be  found  in 
first-class  belting.  Shoulder  stock  is  preferably  cut  crosswise 
of  the  hide,  as  it  stretches  into  better  shape  when  so  cut. 

All  hides  used  for  belting  leather  should  be  carefully  tanned. 


FIG.  626. 

and  afterwards  curried  or  softened  by  "stuffing''  with  hot 
grease,  a  process  which  lubricates  the  fibers  of  the  leather  and 
converts  the  hard,  dry  hide,  as  left  by  tanning,  into  a  strong,  pliable 
leather.  The  hide  is  then  thoroughly  stretched  and  cut  to  re- 
quired widths.  As  all  strips  other  than  the  one  having  the  center 
of  the  hide  as  its  center  will  stretch  more  on  the  one  edge  than 
the  other,  it  is  desirable  to  take  out  most  of  this  stretch  before 
the  belt  is  put  into  use.  It  is  not,  however,  advisable  to  take  out 
all  of  the  stretch,  as  the  belt  is  then  rendered  "dead,"  and  lacks 
that  elasticity  so  desirable  in  a  good  belt. 

The  leather  is  scarfed  to  uniform  thickness  and  by  careful 
working  and  polishing  is  brought  into  the  smooth  uniform  condi- 
tion commonly  found  in  the  commercial  leather  belting.  The 


492  MODERN    MACHINE    SHOP    TOOLS. 

weight  of  the  belt  is  an  important  feature,  a  heavy  belt  being,  as 
a  rule,  more  desirable  than  a  light  one.  Heavy  single  belts  are 
cut  from  selected  hides  with  a  view  to  obtaining  weight.  Belts 
from  lighter  hides  are  frequently  made  heavy  by  excessive  stuffing. 
This  is  not  desirable.  When  belts  are  required  heavier  than  the 
thickest  hides  will  make,  it  is  necessary  to  glue  two  or  more  thick- 
nesses together,  making  "double/'  "triple,"  or  "quadruple"  ply 
belting.  What  is  termed  a  "light  double"  belt  is  made  of  two  thick- 
nesses of  thin  hides,  one  side  unusually  being  belly  or  shoulder 
stock.  The  weight  of  the  "light  double"  belt  is  about  one  and  one 
half  the  weight  of  single  belt.  Double  belt  is  twice  the  weight  of 
single;  triple  three  times  the  weight,  etc.  In  the  making  of 
double  belts  the  strips  should  be  so  placed  that  edges  of  greatest 
stretch  will  come  opposite  so  as  to  average  up  the  stretch  and 
make  good  running  belts.  The  opportunity  for  fraud  in  the 
making  of  leather  belting  and  especially  in  the  heavy  plies  is 
great.  Low  prices  usually  mean  light  weight  or  poor  quality, 
which  is  generally  not  discovered  until  the  belt  begins  to  go  to 
pieces  after  short  service. 

Light  and  heavy  double  belts  are  used  for  transmitting  heavier 
power  than  the  single  belt  will  satisfactorily  stand.  Usually  for 
drive  belts  it  is  better  to  use  a  double  belt  than  a  single 
one  of  greater  width.  Light  double  belts  are  well  adapted  to  use 
as  shifting  belts,  where  there  is  considerable  wear  on  their  edges, 
also  for  shifting  belts  on  cones.  A  double  belt  should  not  be 
used  on  pulleys  of  too  small  diameters,  as  the  short  bend  breaks 
the  joint. 

In  a  piece  of  belting  leather  the  strongest  section  is  on  the  flesh 
side.  The  hair  side  is  relatively  weak,  hard,  and  liable  to  crack. 
For  this  reason  the  hair  side  of  the  belt  should  always  be  run  next 
to  the  pulley,  as  it  brings  the  fibers  on  the  flesh  side,  which  can 
best  resist  the  strain,  under  tension  as  the  belt  passes  over  the 
pulley,  and  the  hair  side,  which  can  least  resist  the  strain,  under 
compression.  Belts  run  in  this  manner  seldom  crack,  while  on 
the  other  hand  if  run  flesh  side  to  the  pulley  transverse  cracks 
are  sure  to  show  up  on  the  hair  side  which  gradually  grow 
deeper  and  eventually  ruin  the  belt.  The  hair  side  of  the  belt 
is  the  smoother,  comes  in  better  contact  with  the  surface  of  the 
pulley  and  by  actual  test  will  transmit  about  25  per  cent  more 
power,  other  conditions  being  equal,  than  when  the  flesh  side  is 
run  next  to  the  pulley. 


BELTING  AND  TRANSMISSION   MACHINERY.  493 

The  ultimate  tensile  strength  of  leather  belting,  depending 
on  its  quality,  varies  through  a -wide  range.  Most  samples  fall 
within  the  limits  of  2,000  to  5,000  pounds  per  square  inch,  with 
1,000  to  2,000  pounds  at  properly  laced  joints.  Cotton  belting 
has  greater  strength  than  leather,  and  when  coated  with  rubber 
clings  to  the  pulley  more  closely  than  leather.  It  is  much  better 
than  leather  for  use  in  damp  places  or  where  subjected  to  material 
changes  in  temperature.  Leather  belting  cannot  be  used  in  places 
where  there  is  dampness,  as  it  starts  the  glued  joints  and  other- 
wise injures  the  belt.  By  a  special  waterproof  treatment  leather 
belting  is  made  to  stand  a  limited  amount  of  dampness,  but  rub- 
ber-covered cotton  will  be  found  preferable  under  such  con- 
ditions. Leather  belting  should  not  be  used  in  temperatures 
higher  than  1 10  degrees. 

The  power  that  can  be  transmitted  by  a  belt  varies,  according 
to  conditions,  through  very  wide  limits,  consequently  fixed  rules 
cannot  be  laid  down  for  the  calculation  of  belt  powers.  As  a  pull 
of  33,000  pounds  through  a  space  of  one  foot  in  one  minute  repre- 
sents one  horse  power  of  work,  a  pull  of  33  pounds  through  a 
space  of  1,000  feet  in  one  minute  would  represent  the 
same  amount  of  work.  By  increasing  the  velocity  or  the 
tension,  the  work  performed  is  correspondingly  increased. 
The  working  strain  on  good  leather  belting  may  be  taken 
at  from  45  to  60  pounds  per  inch  of  width  for  single  belts 
and  at  double  that  amount  for  double  belts  when  the  thickness 
is  double  that  of  the  single  belt.  From  the  above,  a  heavy  single 
belt  running  at  1,000  feet  per  minute  will  transmit  60-33  or  I-^ 
horse  power,  while  a  heavy  double  would  transmit  3.6  horse  power. 
At  4,000  feet  per  minute  these  same  belts  would  transmit  7.2 
and  14.4  horse  power  respectively,  and  if  the  widths  were  in- 
creased to  10  inches  they  would  transmit  72  and  144  horse  power 
respectively.  The  tables  ordinarily  used  give  powers  somewhat 
under  the  above,  a  common  rule  being  to  allow  one  inch  of 
width  at  1,000  feet  per  minute  for  every  horse  power  with  single 
belts  and  one-half  inch  of  width  for  double  belts.  This  rule  gives 
a  most  liberal  margin,  especially  for  single  belts.  Excessively 
tight  belts  should  be  avoided  not  only  because  of  the  injury  to 
the  belt  but  because  of  the  excessive  strains  on  shafting,  boxes, 
and  pulleys.  Covering  the  face  of  the  pulley  with  leather  increases 
the  adhesion  of  the  belt  from  30  to  40  per  cent.  A  cover  of  this 
kind  must  be  carefully  put  on,  for  best  results,  the  leather  from 


494  MODERN    MACHINE    SHOP    TOOLS. 

which  it  is  made  being  scarfed  to  uniform  thickness  and  fitted 
closely  over  the  pulley. 

Whenever  the  character  of  the  work  permits,  leather  belts 
should  be  made  endless  by  beveling  the  ends  and  making  a  glued 
lap  joint.  This  makes  a  strong  joint  that  runs  smoothly  over  the 
pulleys,  and  is  most  important  in  the  case  of  high  speed  belts 
operating  on  pulleys  of  small  diameters.  In  double  belts  the 
joint  should  be  lapped  as  shown  in  Fig.  627.  It  is  not  neccrsary  to 


FIG.  627. 

use  rivets  or  other  fasteners  in  connection  with  the  glued  lap 
joints.  In  fact,  the  best  practice  now  dispenses  with  them  en- 
tirely. In  gluing  the  joint  a  special  belt  glue  should  be  used 
and  applied  hot  to  both  surfaces  in  order  that  it  may  penetrate 
well  into  the  pores  of  the  leather.  The  surfaces  must  be  clamped 
firmly  and  squarely  together  and  given  sufficient  time  to  dry 
well. 

The  lacing  of  belts  is  a  matter  of  much  importance  and  suf- 


FIG.  628. 

ncient  care  is  not  ordinarily  exercised  in  this  work.  The  time- 
honored  method  of  lacing  belts  with  thongs  of  rawhide  has  nearly 
given  over  to  the  better  practice  of  using  wire  lacing,  or  a  limited 
few  of  the  many  patented  belt  fasteners.  The  usual  troubles  with 
fasteners  arise  not  from  the  fastener  itself,  but  from  its  improper 
application.  For  any  kind  of  fastener  the  belt  must  be  cut  square, 
a  try  square  and  not  the  eye  being  depended  upon  for  this  work. 
The  ends  must  be  held  squarely  together  when  the  fastening  is 
made. 


BELTING   AND   TRANSMISSION    MACHINERY. 


495 


Heavy  belts  should,  for  gluing  or  lacing,  be  drawn  together  by 
means  of  the  belt  clamps  shown  in  Fig.  628  in  place  on  the  pulleys ; 
AS  the  edge  of  a  wide,  tight  belt  is  invariably  stretched  when 
run  onto  the  pulleys.  On  the  side  next  to  the  pulley  the  lace 
leather,  wire,  or  fastener  should  run  parallel  with  the  belt's  length, 
and  not  cross  each  other,  as  in  that  case  they  make  a  rough 


PULLEY.  SIDE 


PULLEY  SIDE. 


FIG.  629. 


FIG.  630. 

surface  and  wear  off  very  quickly.  The  holes  should  be  punched 
exactly  opposite  each  other  and  should  be  the  smallest  possible 
that  will  let  the  lacing  through.  In  the  case  of  raw  hide  lacing, 
the  usual  mistake  of  using  too  few  strands  and  too  heavy  a  thong 
should  be  avoided.  A  satisfactory  method  is  shown  in  Fig.  629. 
The  strands  on  the  inner  side  should  be  about  5-8  of  an  inch  apart, 
and  the  staggering  of  the  holes  gives  a  firm  hold  on  the  ends  of 


JJ96  MODERN    MACHINE    SHOP    TOOLS. 

the  belt.  It  is  best  to  lace  from  the  edges  to  the  center,  tying  off 
at  the  center. 

In  Fig.  630  is  shown  the  method  of  lacing  belts  with  wire 
lacing.  The  method  is  practically  the  same  as  with  thongs.  The 
wire  used  is  of  comparatively  high  tensile  strength  and  very 
pliable.  By  cutting  shallow  grooves  between  the  holes  on  the 
pulley  side  of  the  belt  for  the  strands  of  wire  to  lie  in  a  very 
smooth  and  durable  joint  is  made  by  this  means.  The  ends  should 
be  carefully  tied  off  or  otherwise  there  is  danger  of  injuring  the 
hand  in  shifting  the  belt. 

Leather  link  belts,  an  example  of  which  is  shown  in  Fig.  631, 
are  used  to  quite  an  extent  for  certain  classes  of  work.  They  are 
built  up  of  leather  links  hinged  together  by  rods,  as  shown  in  the 
figure.  They  are  very  heavy,  run  smoothly,  transmit  heavy  loads 


per  inch  of  their  width;  will  not  come  unglued  from  dampness, 
wear  the  pins  faster  than  the  leather  and  are  very  high  in  price. 

The  care  of  leather  belting  is  a  subject  which  receives  too 
little  attention.  As  above  mentioned,  avoid  dampness  and  ex- 
cessive heat,  lace  properly  and  run  the  proper  side  to  the  pulley.  If 
the  belt  slips  do  not  dope  it  with  compounds  of  questionable  qual- 
ity, rosin,  soap,  etc.,  but  tighten  it.  If  it  continues  to  slip  after 
it  has  been  made  reasonably  tight  it  is  evident  that  it  is  too  narrow. 
Put  on  a  wider  belt,  or  double  the  thickness  of  the  troublesome 
one. 

As  the  original  "stuffing"  or  lubricant  dries  out,  the  belt  loses 
its  pliability,  wears  rapidly  and  cracks.  Neat's-foot  oil,  tallow  and 
a  few  of  the  prepared  compounds  are  suitable  for  use  on  leather 
belts  for  softening,  lubricating  and  preserving  them.  Mineral 
oils  injure  belts  as  they  penetrate  and  drive  out  the  original  lubri- 
cants. 


BELTING   AND   TRANSMISSION    MACHINERY. 


497 


In  the  majority  of  cases  belts  are  used  to  connect  parallel 
shafts.  When  shafts  rotate  in  the  same  direction,  the  connecting 
belt  is  called  an  "open"  belt,  and  when  they  rotate  in  opposite 
directions  it  is  called  a  "crossed"  belt.  The  arc  of  contact  is  that 
portion  of  the  pulley's  surface  covered  by  the  belt.  It  is  evident 
that  the  "arc  of  contact"  is  greater  with  the  crossed  then  with 
the  open  belt,  and  that  a  crossed  belt  will,  other  conditions  being 
equal,  transmit  more  power  than  an  open  one.  Wide  crossed 
belts  should  be  avoided  in  cases  where  the  shafts  are  close  to- 
gether. 

The  adhesion  of  the  belt  to  the  pulley  is  dependent  upon  the 
condition  of  the  belt  and  pulley  surfaces,  and  the  weight  and 
tension  of  the  belt.  If  the  shafts  are  close  together  the  weight 
of  the  belt  is  small  and  its  tension  must  be  greater  in  order  to 
transmit  a  given  power.  When  the  shafts  are  reasonably  far  apart 


FIG.  632. 

the  weight  of  the  belt  adds  much  to  its  adhesion  to  the  pulleys. 
For  narrow  belts  10  to  15  feet  are  good  centers  when  the  belts 
are  operating  over  pulleys  of  comparatively  small  diameters.  With 
wider  belts  operating  over  larger  pulleys  20  to  25  feet  should, 
if  possible,  be  allowed,  and  for  heavy  drive  belts  30  to  50  feet 
are  usual.  Too  long  a  belt  is  liable  to  whip,  especially  in  cases 
where  the  power  transmitted  is  not  perfectly  steady.  Whipping 
injures  the  belt  and  causes  severe  strains  on  the  machinery. 

When  possible  the  lower  side  of  the  belt  should  be  the  ten- 
sion or  driving  side,  making  the  condition  as  shown  in  Fig.  632. 
If  the  top  side  is  the  driving  side,  the  condition  becomes  as  shown 
in  Fig.  633.  The  arc  of  contact  is  much  greater  in  the  first  case, 
and  as  a  consequence  a  more  powerful  drive  is  obtained  than  (in 
the  latter  case,  all  other  conditions  being  equal. 

When  parallel  shafts  in  a  vertical  plane  are  connected  as  shown 
in  Fig.  634,  the  tension  must  be  much  greater  than  in  the  cases 


498 


MODERN    MACHINE    SHOP    TOOLS. 


above  referred  to,  inasmuch  as  the  weight  of  the  belt  tends  to 
hold  it  away  from  the  lower  pulley.  When  the  difference  in 
diameter  between  the  pulleys  is  great,  a  heavy  belt  on  fairly  long 
centers,  run  as  shown  in  Fig.  635,  should  be  used  when  possible. 


FIG.  634. 


FIG.  635. 


BELTING    AND   TRANSMISSION    MACHINERY. 


499 


When  the  centers  are  close  and  a  tightener  becomes  necessary 
it  should  always  be  put  on  the  slack  side  of  the  belt  as  shown  in 
Fig.  636.  This  location  puts  a  minimum  amount  of  pressure 
on  the  tightener  and  its  bearings.  Tightener  pulleys  should  be 
of  liberal  diameter  in  order  to  prevent  noise  and  wear  due  to 
high  rotation  and  injury  to  the  belt  due  to  a  short  reverse  bend. 
In  Fig.  637  is  shown  a  method  of  driving  two  parallel  shafts 


FIG.  637. 

from  a  third  parallel  with  them.    One  belt  runs  on  top  of  the  other 
on  the  driving  pulley. 

In  Fig.  638  is  shown  what  is  generally  known  as  a  quarter 
turn  belt,  commonly  used  for  connecting  shafts  at  right  angles 
with  each  other  and  in  different  planes.  The  location  of  the  pulleys 
must  be  such  that  the  belt  leads  from  the  face  of  one  to  the 
center  of  the  face  of  the  other.  With  this  arrangement  the  direc- 


FIG.  638. 

tion  of  rotation  cannot  be  reversed.  The  pulleys  should  have 
liberally  crowned  faces  and  pulley  A  should  have  a  face  il/2 
times  the  width  of  the  belt.  The  centers  must  be  reasonably  far 
apart  to  give  good  results. 

When  shafts  are  in  the  same  plane  and  at  an  angle  with  each 
other  they  may  be  connected  as  shown  in  Fig.  639  by  what  is 
called  a  quarter-twist  belt  operating  over  mule  pulleys.  The  pul- 
leys should  all  be  of  the  same  size  and  well  crowned.  By  having 


500 


MODERN    MACHINE    SHOP    TOOLS. 


the  mule  pulleys  so  mounted  that  their  axes  may  be  inclined  from 
each  other,  the  driving  pulley  may  be  made  of  a  larger  or  smaller 
diameter  than  the  driven. 

When  belts  run  on  straight-faced  pulleys  it  is  necessary  to 
guide  them  on  the  pulleys  in  some  manner,  as  otherwise  they  are 
quite  apt  to  run  off,  and  especially  so  if  the  shafts  are  not  exactly 
parallel  with  each  other.  In  such  cases  a  pair  of  fingers,  between 
which  the  belt  runs,  is  placed  a  short  distance  from  the  driven 
pulley  on  the  side  of  the  belt  which  leads  onto  the  pulley.  Flanges 
on  the  edges  of  the  pulley  are  frequently  employed.  As  the  usual 


FIG.  639. 


form  of  flange  guides  the  belt  after  it  makes  its  bearing  on  the 
face  of  the  pulley,  the  destructive  action  of  the  flange  on  the  edge 
of  the  belt  is  great,  due  to  the  resistance  of  the  belt  to  a  change 
in  direction  after  it  has  come  in  contact  with  the  pulley's  face. 
This  action  is  reduced  somewhat  by  under  cutting  the  face  of 
the  flange  so  that  only  its  outer  portion  comes  in  contact  with  the 
edge  of  the  belt,  thus  virtually  forming  a  guide  at  some  distance 
from  where  the  belt  comes  in  contact  with  the  pulley's  face. 

When  belts  are  not  to  be  shifted  the  usual  method  of  guiding 
is  by  crowning  the  face  of  the  pulleys.     The  belt  then  tends  to  run 


BELTING   AND   TRANSMISSION    MACHINERY. 


501 


on  the  high  part  of  the  pulley  for  the  following  reasons:  If,  as 
shown  in  Fig.  640,  the  belt  is  forced  to  one  side,  the  edge  a  be- 
comes stretched,  making  that  part  of  the  belt  in  contact  with  the 
pulley's  surface  of  conical  shape,  with  the  edge  a  traveling  faster 
than  the  edge  b,  thus  causing  it  to  run  in  the  direction  of  the 
arrow  and  to  center  itself  on  the  pulley. 

When  the  shafts  are  parallel  a  belt  always  runs  to  the  high 
part  of  the  pulley.  If,  however,  the  shafts  are  not  parallel  and  the 
high  side  is  caused  by  the  position,  and  not  the  shape  of  the 


•\ 


FIG.  640. 


FIG.  641. 


pulley,  as  shown  in  Fig.  641,  the  belt  runs  to  the  low  edge,  inas- 
much as  it  passes  onto  the  pulley  in  a  spiral  direction  and  all 
points  when  they  first  come  in  contact  with  the  pulley's  surface 
are  carried  in  the  direction  of  the  pulley's  rotation  as  indicated 
by  the  arrow. 

When  the  distance  between  shafts  becomes  great,  leather  belt- 
ing is  no  longer  suitable  for  transmitting  the  power  and  con- 
necting shafts  or  rope  belting  is  substituted.  The  connecting  shaft 
method  is  but  little  used  and  is  well  adapted  only  when  the  shafts 


502  MODERN    MACHINE    SHOP    TOOLS. 

are  in  the  same  horizontal  plane,  the  connection  usually  being^ 
made  by  two  quarter-twist  belts  as  shown  in  Fig.  639. 

The  use  of  rope  transmission  has  nearly  superseded  the  shaft 
method  because  of  its  higher  efficiency  and  greater  flexibility.  It 
is  difficult  to  conceive  of  any  combination  of  shafting  as  to  posi- 
tion, angles,  etc.,  that  cannot  be  successfully  connected  up  by 
rope  drives. 

As  wire  rope  transmissions  are  not  frequently  used  in  shop 
drives,  only  those  cases  pertaining  to  cotton  and  manila  rope  drives 
will  be  considered. 

For  the  transmission  of  power,  only  the  best  of  cotton  and 
manila  rope  is  suitable.  Cotton  rope  because  of  its  greater  flexi- 
bility is  better  adapted  for  service  on  small  diameter  sheaves  than 
manila  rope.  It  is  not  as  durable  as  the  manila,  has  not  the  ten- 
sile strength,  is  harder  to  splice,  and  higher  in  first  cost. 

The  manila  rope  used  for  transmission  purposes  should  be  of 
the  best  possible  quality,  manufactured  from  long  fiber  manila 
which  has  been  carefully  cleaned  and  selected.  The  smaller  ropes 
are  made  of  three  strands,  with  four  and  six  strands  for  the  heavier 
ropes.  The  four  and  six  strand  ropes  have  a  central  core  around 
which  the  strands  are  laid.  The  principal  wear  in  transmission 
rope  comes  from  the  continuous  rubbing  of  the  fibers  together.  To 
overcome  this  has  been  the  great  study  on  the  part  of  the  transmis- 
sion rope  manufacturers.  The  free  use  of  a  lubricant,  as  plumbago 
and  tallow,  on  the  core  and  inner  strands  of  the  rope  serves  to 
soften  and  reduce  the  wear  on  the  fiber. 

The  splicing  of  transmission  rope  is  a  most  important  opera- 
tion and  one  upon  which  the  success  of  the  drive  very  largely 
depends.  The  splice  is  the  weakest  point  in  the  rope,  yet  if  prop- 
erly made  it  will  wear  well  and  seldom  gives  trouble.  It  is  quite 
necessary  that  the  splice  be  a  long  one,  and  wher^.  finished  of  the 
same  diameter  as  the  balance  of  the  rope.  The  ends  must  be  so 
secured  that  they  will  not  wear  or  cause  their  covering  strands 
to  wear  off,  thus  freeing  the  ends  enough  to  allow  them  to  whip 
out  as  they  pass  over  the  sheaves.  Old  sailors  do  not  know  how 
to  splice  transmission  rope,  and  should  not  be  called  upon  for 
this  service.  A  careful  mechanic,  following  instructions,  usually 
has  no  trouble  in  making  a  satisfactory  splice.  It  is  extremely  dif- 
ficult to  splice  a  piece  of  new  rope  into  an  old  one,  as  the  stretch 
is  out  of  the  old  rope,  which  causes  it  to  pull  away  from  the  new. 
There  is  also  considerable  difference  in  diameters.  In  such  cases 


BELTING    AND    TRANSMISSION    MACHINERY. 


503 


the  new  rope  should,  if  possible,  be  thoroughly  stretched  before 
putting  it  in,  and  the  old  rope  laid  slack  in  the  splice,  an  amount 


FIG.  642A. 


FIG.  642D. 


FIG.  642B. 


FIG.  6420. 


FIG.  642E. 


wholly  dependent  upon  the  judgment  of  the  workman,  to  allow  for 
the  stretch  in  the  new  rope. 

The  illustrations  in  Fig.  642  and  the  instructions  following  are 


504  MODERN    MACHINE    SHOP    TOOLS. 

those  furnished  by  the  Link  Belt  Machinery  Company  for  making 
standard  rope  splices. 

TO    SPLICE    A    FOUR-STRAND    MANILA    ROPE. 

Tie  pieces  of  twine  a  and  b  around  the  rope  to  be  spliced  one- 
half  the  length  of  the  splice  from  the  ends.  (See  table  for  length 
of  splice.)  Unlay  the  strands  of  each  rope  back  to  the  twine. 
Butt  or  mesh  the  ropes  together  and  twist  corresponding  pairs 
together  to  keep  them  from  being  tangled,  as  shown  in  A.  Cut  a. 
Unlay  strand  8  and  carefully  lay  strand  7  in  its  place  for  a  dis- 
tance equal  to  three-fourths  its  length.  Strand  5  is  next  inlaid 
about  one-quarter  its  length  and  strand  6  laid  in  its  place.  The 
ends  of  the  cores  are  now  cut  off  so  they  just  meet.  Unlay  strand 
I  three-quarters  of  its  length,  laying  strand  2  in  its  place.  Unlay 
strand  4  one-quarter  of  its  length,  laying  strand  3  in  its  place. 

Cut  all  the  strands  off  to  a  length  about  20  inches  for  con- 
venience. The  rope  will  now  have  the  appearance  shown  in  B. 
Each  pair  of  strands  is  now  subjected  to  the  following  operation. 
(See  figure  C.) 

Split  strands  7  and  8  in  halves  from  the  ends  to  the  point  of 
meeting  at  the  body  of  the  rope.  The  end  of  each  half  strand  is 
now  whipped  with  a  small  piece  of  twine.  Take  half  strand  7a  and 
corresponding  half  strand  8a  and  tie  them  in  a  single  knot,  draw- 
ing the  knot  down  firm  and  taking  care  the  yarns  lie  in  so  that 
the  knot  has  the  same  appearance  as  the  rest  of  the  rope.  We 
now  pass  on  to  D. 

The  rope  is  now  opened  by  inserting  a  marlinspike  between 
strands  8  and  the  other  two  strands  at  a  point  just  beyond  the 
knot.  Half  strand  8b  is  pulled  out  and  half  strand  7a  pulled  in, 
in  place  of  half  strand  8b ;  care  being  taken  in  pulling  in  half 
strand  7a  to  keep  the  rope  smooth  and  firm,  also  to  keep  the 
yarns  twisted  the  same  amount  as  in  the  rest  of  the  rope.  Con- 
tinue this  operation  until  about  one-quarter  of  half  strand  7a  is 
used.  Then  drop  a  yarn  from  each  strand  by  pulling  out  of 
half  strand  8b  less  one  yarn  and  pulling  in  half  strand  7a  less 
one  yarn,  thus  keeping  the  number  of  yarns  in  the  strand  the 
same  and  the  rope  the  same  size  as  at  any  point.  Go  on  as  before, 
dropping  a  yarn  at  every  second  opening  until  all  of  the  yarns  are 
dropped.  The  dropped  yarns  are  laid  over  the  strand  being 
worked  on  and  pulled  under  the  adjacent  strands  respectively 
at  the  time  they  are  dropped  by  opening  the  rope.  They  are  then 


BELTING    AND    TRANSMISSION    MACHINERY.  505 

cut  off  to  about  2  inches  long.  Half  strands  8a  and  7b  are  treated 
in  like  manner,  going  in  the  opposite  direction. 

The  ends  of  the  yarns  left  sticking  out  will  partly  be  drawn 
into  the  body  of  the  rope  and  partly  worn  off  in  a  short  time,  so 
that  the  locality  of  the  splice  can  hardly  be  detected. 

In  the  larger  ropes  from  one  inch  up,  two  yarns  may  be 
dropped  at  a  time  when  that  stage  of  the  splice  has  been  reached, 
as  it  would  make  too  long  a  splice  to  drop  them  one  at  a  time. 

Size  of  Rope.  Length  of  Splice. 

y&  inch  12  feet 

y*  "•  13  " 

n  "  14  " 

i  i4  " 

1/8      "  IS      " 

i'/4    "  16    " 

H/s    "  18    " 

ll/2        "  18        " 

13/4      "  20      " 

There  are  two  systems  of  rope  transmission  in  common  use — 
the  "multiple  system"  and  the  ''continuous  system."  The 
''multiple  system"  consists  of  independent  ropes  running 
side  by  side,  while  the  "continuous  system"  consists  of  one 
rope  wound  around  the  pulleys  several  times.  The  "multiple 
system"  is  much  used  for  transmitting  heavy  powers,  and  while 
not  so  adaptable  to  many  special  drives,  possesses  some  important 
advantages  over  the  "continuous  system."  In  the  case  of  a  rope 
failure  it  can  be  removed,  the  balance  of  the  ropes  carrying  the 
load  until  the  repair  can  be  conveniently  made.  As  idlers  and 
tension  pulleys  are  not  ordinarily  required,  the  rope  is  not  sub- 
jected to  a  continuous  reverse  bending,  thus  making  it  more  dur- 
able. In  Fig.  643  is  shown  an  example  of  the  "multiple  system" 
of  rope  driving. 

In  the  "continuous  system,"  an  example  of  which  is  shown 
in  Fig.  644,  a  single  rope  is  used,  it  being  wrapped  continuously 
about  the  drive  and  driven  sheaves  with  a  tension  idler  to  take  up 
the  slack.  The  use  of  the  tension  carriage  is  necessary  in  order 
to  take  up  the  stretch  in  the  rope  and  maintain  a  uniform  tension 
in  it.  The  position  of  the  tension  carriage  should  be  such  that  it 
takes  care  of  the  slack  at  the  point  where  it  naturally  accumulates. 
In  the  example  shown  the  last  strand  from  the  driver  leads  over 


5o6 


MODERN    MACHINE    SHOP    TOOLS. 


an  idler  sheave  mounted  at  the  side  of  the  driven  sheave.  The 
tension  is  taken  from  this  sheave  back  to  the  opposite  groove 
on  the  driven  by  means  of  the  tension  sheave,  the  axis  of  which 
is  sufficiently  inclined  to  lead  the  rope  properly. 

The  applications   of  the  rope  drive  are   many,   and   for  the 


FIG.  643. 

smooth,  quiet  transmission  of  power  it  has  become  a  popular 
method.  Perfect  alignment  of  sheaves  is  not  necessary,  and 
shafts  may  be  run  at  any  angle  with  each  other  and  at  any  dis- 
tance within  reasonable  limits. 

The  sheave  pulley  is  one  in  which  deep  grooves  are  cut  in  its 
rim  to  receive  the  wraps  of  the  rope.     They  are  made  of  cast  iron 


FIG.  644. 


with  the  surfaces  of  the  grooves  very  carefully  polished,  as  any 
roughness  wears  the  rope  unduly.  For  driving  and  driven  sheaves 
the  accepted  form  of  groove  is  the  one  shown  in  Fig.  645  at  A. 
The  angle  of  the  sides  of  the  groove  at  the  pitch  line  a  a  is  45 
degrees  with  each  other.  The  sides  are,  however,  slightly  con- 
cave in  section,  which  produces  a  rolling  motion  in  the  rope  re- 


BELTING   AND   TRANSMISSION    MACHINERY. 


507 


suiting  in  a  more  uniform  wear  on  the  rope  than  when  it  runs 
without  rolling. 

The  width  of  the  groove  at  the  pitch  line  is  such  that  the 
rope  bears  on  the  sides,  thus  wedging  in  and  causing  a  high  fric- 
tional  resistance  to  slipping.  When  used  as  an  idler  the  bottom 
of  the  groove,  as  shown  at  B,  is  semicircular,  the  radius  being 
equal  to  or  slightly  greater  than  the  radius  of  the  rope  when 
new. 

When  the  sheave  has  two  or  more  grooves  it  is  very  important 
that  they  be  of  the  same  shape,  size,  and  diameter  in  order  to 
avoid  any  slipping  or  "creeping"  of  the  rope.  Sheaves  smaller 
in  diameter  than  30  times  the  diameter  of  the  rope  should  not  be 
used  with  ropes  under  ij4  inch.  With  ropes  over  ij4  inch  in 


FIG.  645. 

diameter  the  sheave  should  not  be  less  in  diameter  than  40  times 
the  rope  diameter.  The  larger  the  sheave  the  less  the  bending  of 
the  rope  and  consequent  wear  upon  it. 

The  usual  speed  at  which  ropes  are  operated  is  between  3,000 
and  4,000  feet  per  minute.  When  the  speed  exceeds  4,000  feet, 
but  little  gain  can  be  had  in  the  power  transmitted  up  to  5,000 
fefct,  and  above  that  speed  the  power  tfansmitted,  due  to  the  ex- 
cessive centrifugal  action,  falls  off  rapidly. 

The  table  in  Chapter  XXXIV,  compiled  by  C.  W.  Hunt,  gives 
the  horse  power  of  "Stevedore"  transmission  rope  at  various 
speeds. 

Shafting  as  universally  used  at  the  present  time  for  power 
transmission  purposes  is  of  mild  steel  finished  smooth,  round  and 
true,  either  by  turning  or  by  cold  rolling.  Turned  steel  shafting^ 


MODERN    MACHINE    SHOP    TOOLS. 


runs  in  sizes  1-16  inch  under  the  common  sizes,  as  I  15-16,  2  3-16, 
2  7-16,  etc.,  it  having  been  finished  from  black  stock  of  2,  2^ 
and  2^4  inches  diameter,  respectively,  by  turning  in  a  special  shaft- 
ing lathe.  The  final  true  surface  on  turned  shafting  is  obtained  by 


FIG.  646. 

passing  a  hollow  reamer  or  shafting  burr  over  it,  or  by  a  final 
rolling  process.  Cold  rolled  shafting  is  given  its  final  finish  by  a 
cold  rolling  process  which  leaves  a  true  smooth  surface  and  also 
intensifies  and  stiffens  the  material.  When  a  number  of  lengths 

o 

of  shafting  are  to  be  connected  together  a  suitable  coupling  must 


FTG.  647. 

be  employed.  A  flanged  face  coupling  is  shown  in  Fig.  646.  These 
should  be  fitted  to  the  ends  of  the  shaft  and  the  faces  turned  in 
place,  thus  insuring  faces  at  right  angles  to  the  axis  of  the  shaft 
-and  a  true  connection.  Compression  couplings  are  of  numerous 
forms,  many  possessing  good  points.  In  Fig.  647  is  shown  a 


BELTING    AND   TRANSMISSION    MACHINERY. 


509 


simple  and  effective  compression  coupling.  It  consists  of  two 
semicircular  shells  fitted  and  bolted  together.  The  shaft  ends 
come  together  in  the  center  and  are  held  concentrically  true.  A 
key  properly  fitted  makes  a  positive  drive  and  a  pin  projecting  a 
short  way  into  the  shaft  at  each  end  of  the  coupling  prevents  the 
shafts  from  pulling  out  of  the  coupling. 

Shafting  lengths  should  be  so  selected  as  to  bring  the  couplings 
close  to  the  bearings.    For  example,  if  bearings  are  eight  feet  apart 


FIG.  648. 

the  shafting  lengths  should  be  8,  16  or  24  feet.  When  it  is  fre- 
quently desirable  to  disconnect  two  lengths  of  shafting  a  dental 
coupling,  Fig.  648,  may  be  employed.  The  construction  is  evi- 
dent. The  end  of  one  shaft  should  extend  into  the  opposite 
coupling  enough  to  hold  the  ends  concentric.  A  bearing  should  be 
provided  on  each  side  of  this  form  of  coupling.  They  cannot  be 
operated  when  the  shafts  are  in  motion. 

The  universal  coupling,  Fig.  649,  is  suitable  for  connecting 


FIG.  649. 

shafts  which  are  at  a  small  angle  with  each  other.  They  will  oper- 
ate at  an  angle  of  25  degrees,  but  are  not  well  suited  to  the  pur- 
pose when  the  angle  exceeds  10  or  15  degrees. 

Pulleys  for  power  transmission  purposes  are  of  two  classes, 
whole  and  split.  The  whole  pulley  is  made  in  a  single  piece  and 
must  be  put  on  its  shaft  from  the  end.  The  split  pulley  is  made 
in  halves  and  can  be  put  on  the  shaft  at  any  point  in  its  length. 
Pulleys  are  constructed  of  wood,  cast  iron  and  wrought  iron  or 


MODERN     MACHINE    SHOP    TOOLS. 


steel.  The  wood  pulley  is  built  up  of  small  sections  of  hard  wood, 
well  glued  and  secured  together,  the  whole  being  turned  true. 
They  are  provided  with  bushings  for  any  size  of  shaft  and  are 
secured  to  the  shaft  by  a  clamp  hub.  They  are  lighter  than  cast 
iron  pulleys  and  are  well  adapted  to  high  speed  work.  They  are 
little  used  in  machine  shops. 

Cast  iron  pulleys  are,  when  of  large  diameter,  made  in  sections 
because  of  the  severe  shrinkage  strains  in  the  castings.  They 
should  always  be  balanced,  and  when  of  extra  wide  face  they 
should  be  provided  with  double  sets  of  arms  as  shown  in  Fig.  650. 
The  steel  rimmed  pulley  shown  in  Fig.  651  is  coming  into  quite 


PIG.  650. 


FIG.  651. 


•extensive  use.  It  consists  of  a  cast  iron  center  or  spider  with  a 
sheet  steel  rim  riveted  to  the  arms.  It  is  a  light,  strong  pulley,  free 
from  strains  and  well  suited  to  all  classes  of  work. 

Pulleys  are  "tight"  or  "loose,"  depending  on  whether  they  are 
to  be  secured  to  the  shaft  or  are  to  turn  freely  upon  it.  They  are 
"straight"  or  "crowned,"  depending  on  whether  they  are  to  carry 
shifting  or  non-shifting  belts.  When  used  for  very  heavy  service 
the  rims  are  made  extra  heavy. 

When  it  is  necessary  to  frequently  stop  or  start  a  pulley  with- 
out stopping  the  shaft  a  clutch  pulley  is  employed.  In  Fig.  652  is 
shown  a  cut  of  such  a  pulley.  The  clutch  is  keyed  to  the  shaft 
and  the  pulley  runs  free  upon  the  shaft  when  the  clutch  is  dis- 


BELTING    AND    TRANSMISSION    MACHINERY.  511 

engaged  from  it,  as  shown  in  the  figure.  By  sliding  the  sleeve 
toward  the  hub  of  the  clutch  the  toggle  joint  closes  the  jaws 
firmly  onto  the  smooth  rim  attached  to  the  pulley,  thus  locking 
the  two  firmly  together.  There  are  many  forms  of  clutches,  differ- 
ing widely  in  design,  made.  One  of  the  most  important  features 
of  a  good  clutch  pulley  is  a  long  bushing  in  the  pulley  with  suit- 
able provisions  for  its  thorough  lubrication. 

Shafting    must   be    carried    in    suitable    bearings,    which    are 
mounted  in  what  are  known  as  hangers.     A  hanger  is  a  frame, 


FIG.  652. 

usually  of  cast  iron,  which  carries  the  bearing  and  is  suspended 
from  the  ceiling.  The  same  frame  when  set  on  the  floor  becomes  a 
floor  stand,  and  when  made  to  fasten  to  a  post  or  the  wall  is  called 
a  post  hanger.  Wall  boxes  are  made  to  set  in .  the  wall  in 
cases  where  the  shaft  passes  through  the  wall. 

The  most  important  feature  of  all  hangers  is  the  box  or  bear- 
ing. They  should  be  lined  with  a  good  grade  of  bearing  metal 
and  preferably  provided  with  some  form  of  self-oiling  device.  In 
Pig  653  is  shown  a  self-oiling  hanger  bearing.  The  form  is  known 


512  MODERN    MACHINE    SHOP    TOOLS. 

as  a  ring  oiling  bearing ;  the  ring  shown  running  on  the  shaft  car- 
ries the  oil  from  the  reservoir  to  the  bearing.  Chains  and  wicks 
are  used  for  this  purpose  in  other  forms. 

The  proper  erecting  of  line  shafting  requires  good  care  and 
judgment  on  the  part  of  the  workman.  The  perfect  alignment 
of  the  shafting  and  proper  setting  of  bearings  means  much  as  to 
the  efficiency  of  the  plant.  Poorly  lined  shafting  absorbs  much 
power,  causes  undue  wear  and  trouble  with  the  boxes  and  incor- 
rect running  belts. 

When  properly  lined  it  must  not  be  assumed  that  the  alignment 


Sectional  View. 


End  View. 
FIG.  653. 

will  always  remain  correct.  The  pull  of  belts ;  the  spring  of  tim- 
bers due  to  changes  in  load  put  upon  the  floors ;  the  warping  of 
timbers  due  to  atmospheric  condition;  the  loosening  of  bolts  and 
shimmings  due  to  vibration,  caused  by  poorly  balanced  pulleys, 
all  tend  to  affect  the  alignment  and  make  occasional  surveys  of 
the  line  shaft  quite  necessary.  • 

The  quickest  and  most  satisfactory  method  of  lining    is    by 
means  of  the  surveyor's  transit.     If  the  two  ends  of  the  line  are 


BELTING    AND    TRANSMISSION     MACHINERY.  513 

determined,  mark  these  points  with  copper  tacks  driven  in  the 
floor  and  bearing  a  center  punch  mark  at  the  correct  point.  Set 
the  transit  over  one  of  these  points  and  line  it  to  the  correspond- 
ing point  at  the  other  end  of  the  line  and  next  establish  as  many 
points  in  the  line  on  the  floor  as  there  are  hangers.  The  points 
should  be  just  outside  the  hanger  bearings  and  the  distance  from 
point  to  point  should  be  found  by  tape  measurement.  By  dropping 
a  plumb  line  over  the  side  of  the  shaft  at  each  point  of  its  support 
and  adjusting  the  hanger  until  the  plumb  centers  over  the  marked 
tack  in  the  floor  the  horizontal  alignment  is  obtained.  The  vertical 
alignment  is  next  obtained  by  taking  level  readings  on  a  rod  held 
vertically  against  the  under  side  of  the  shaft,  the  hangers  being 
adjusted  until  all  readings  are  alike. 

When  the  only  apparatus  to  hand  is  a  spirit  level,  a  straight 
edge  and  plumb  bobs,  the  following  method  may  be  employed.    It 


• 

1 

. 

I 
1 

1 

j 

1                             ( 

f3                           T 

T                      T 

^w$^§^s^^?$^^ 

^^^^NSJJ;^^         , 

- 

FIG.  654. 

should,  however,  be  noted  that  the  ordinary  level  is  quite  unsuit- 
able for  this  class  of  work.  An  accurate  one  must  be  used.  The 
correct  end  points,  having  been  determined  on  the  floor  as  in 
the  former  case,  stretch  a  strong  fine  line  tightly  over  these  points 
and  just  clearing  the  floor ;  establish  the  other  points  by  this  line, 
and  plumb  the  shaft  to  the  points  so  found  for  horizontal  adjust- 
ment. For  the  vertical  adjustment  drive  a  small-headed  nail  a 
short  distance  in  the  floor  by  the  side  of  the  tack  representing  one 
of  the  end  points.  As  the  plumbing  was  from  the  side  of  the 
shaft  and  the  floor  points  are  consequently  one-half  the  shaft 
diameter  from  the  vertical  line  through  the  center  of  the  shaft,  the 
nail  should  be  located  from  the  point  in  the  direction  that  will 
bring  it  in  the  vertical  line  referred  to.  Move  to  the  next  point 
and  locate  a  nail  as  at  the  first  point.  Drive  this  nail  in  until  an 
accurate  straight  edge  resting  on  its  head  and  the  head  of  the 
first  nail  shows  perfectly  level  with  the  second  and  continue  for 
the  entire  number  of  points,  thus  giving  a  level  line  of  nail  heads 


514  MODERN    MACHINE    SHOP    TOOLS. 

under  the  center  of  the  shaft.  Next  adjust  a  tram  to  the  exact 
distance  between  the  top  of  the  first  nail  head  and  the  bottom  of  the 
shaft  and  adjust  the  shaft  vertically  at  all  other  points  to  just  touch 
the  tram.  It  is  usually  advisable  to  tram  the  two  ends  of  the  shaft 
first,  locating  the  hangers  at  the  ends,  so  the  shaft  comes  within 
the  adjustment  of  the  boxes.  This  method  is  illustrated  in  Fig. 
654,  and  makes  a  simple  and  reliable  method. 

Another  method,  not  so  reliable  as  the  above,  is  as  follows  :  For 
the  horizontal  adjustment,  drop  a  plumb  line  from  the  side  of  the 
shaft  at  each  bearing,  and  standing  at  the  end  of  the  shaft  direct 
the  necessary  adjustments  to  make  all  of  the  lines  appear  as  one 
single  line  to  the  eye.  For  the  vertical  adjustment  begin  at  one 
end  of  the  line,  place  the  level  on  the  shaft  and  adjust  the  second 
bearing  until  the  first  section  shows  level.  Move  to  the  second 
section  and  adjust  the  third  bearing  until  that  section  is 
level,  and  in  like  manner  carry  the  level  through  the  entire  length 


.?*•«<*  */* 


of  the  shaft.  If  in  this  method  it  is  difficult  to  keep  the  plumbs 
from  swaying,  immerse  each  bob  in  a  bucket  of  water,  which  will 
aid  much  in  bringing  them  to  rest. 

When  shafts  are  to  be  made  parallel  with  each  other  it  is 
usually  better  to  establish  points  on  the  floor  and  work  from  these 
than  to  attempt  to  tram. a  measure  in  mid  air.  When  shafts  on 
different  floors  are  to  be  made  parallel  the  plumb  line  must  be  car- 
ried through  a  hole  in  the  floor,  being  careful  that  the  line  does  not 
touch  the  sides  of  the  hole. 

The  above  methods  are  applicable  to  most  cases  found  in 
practice. 

A  jack  shaft  is  usually  a  short  shaft  which  receives  the  full 
power  from  the  motor  and  distributes  it  to  the  other  shafts. 

Machine  shop  line  shafts  are  usually  speeded  at  from  125  to 
150  revolutions  per  minute  and  wood  shop  lines  at  from  250  to 


BELTING    AND    TRANSMISSION    MACHINERY.  515 

300.  The  comparatively  low  speed  for  machine  shop  lines  is  made 
.necessary  in  order  to  use  drive  pulleys  of  fairly  good  diameter 
for  the  slow  speed  machine  tool  counter  shafts. 

It  is  always  best  when  possible  to  apply  power  to  a  line  shaft 
as  near  its  center  as  possible.  Heavy  drive  pulleys  should  be 
placed  close  to  the  hangers,  and  the  belts  should  lead  in  opposite 
directions  as  much  as  possible,  in  order  to  balance  up  those  strains 
which  tend  to  throw  the  shaft  out  of  alignment. 

In  calculating  the  speed  of  pulleys  the  following  ratio  may  be 
employed. 

Diameter  of  driver     Revolutions  of  driven 


Diameter  of  driven     Revolutions  of  driver 

Take  for  example  Fig.  655.  The  pulleys  A,  B,  C  and  D  are 
respectively  40,  10,  60  and  8  inches  in  diameter,  and  the  shafts 
make  100,  400  and  3,000  revolutions  per  minute.  This  constitutes 
a  compound  drive.  Consider  each  drive  separately.  Assume  A  as 
the  driver  of  the  first  pair  and  C  the  driver  of  the  second  pair. 
B  and  D  are  the  driven.  If  A  and  its  revolutions  and  the  diameter 
of  B  are  given  to  find  the  revolutions  of  B. 

40       Revolution  of  B  40 

— ,  revolution  of  B  =  100  X  -   =  400 

IO  100  10 

If  D  must  make  3.000  revolutions  and  its  diameter  is  assumed 
as  8  inches,  then  to  find  diameter  of  C  we  get 

Diameter  C       3000  3000       240 

= ,  diameter  of  C  =  8X =  — =60 

8  400  400         4 

In  any  case  multiplying  the  diameter  of  one  pulley  by  its  revolu- 
tions and  dividing  the  product  by  the  diameter  or  revolutions  of  the 
other  pulley  will  give  the  revolutions  or  diameter  of  the  second 
pulley,  as  the  case  may  be. 

Tables  giving  horsepower  and  other  tables  pertaining  to  shaft- 
ing and  belting  are  given  in  Qiapter  XXXIV. 

The  electrical  transmission  of  power  is  now  being  very  largely 
employed,  especially  in  cases  where  the  distances  are  great.  The 
convenience  of  the  system  has  made  it  a  very  popular  one.  The 


5l6  MODERN    MACHINE    SHOP    TOOLS. 

small  power  user  can  buy  his  power  from  the  central  power  station ; 
and  the  large  plants,  requiring  power  in  widely  separated  build- 
ings, can  concentrate  their  engines  and  generators  in  one  station 
and  distribute  the  power  to  any  required  number  of  motors  operat- 
ing the  various  line  shafts.  It  is  usual  to  put  a  separate  motor 
on  each  line  and  to  hold  the  length  of  the  line  with- 
in reasonable  limits.  This  makes  possible  the  shutting 
down  of  any  one  line  for  repairs  or  other  purposes  with- 
out affecting  the  balance  of  the  plant,  a  condition  frequently  of 
great  value.  The  concentrating  of  the  power  into  one  plant  and 
the  employment  of  large  units  add  much  to  the  efficiency  of  operat- 
ing over  several  small  units  scattered  about  the  plant.  The  losses 
in  generators,  motors  and  line  usually  reduces  the  mechanical 
efficiency  of  the  system  to  about  80  per  cent,  of  the  power  devel- 
oped by  the  engine.  Belts,  rope  and  shafting  are  more  efficient 
for  short  transmission,  but  when  the  distances  become  great,  the 
electrical  transmission  leads  in  points  of  efficiency,  cost,  safety  and 
convenience. 

The  application  of  motors  directly  to  machine  tools  is  coming 
into  quite  extensive  use.  The  advantages  are  chiefly  in  the  doing 
away  with  the  overhead  work,  thus  leaving  an  unobstructed 
passage  for  the  operating  of  cranes  and  carriers.  It  is  also  possible 
to  set  the  machine  in  any  position  regardless  of  the  direction  of 
the  line  shaft. 

The  motors  used  for  this  class  of  work  are  either  of  the  con- 
stant or  variable  speed  class.  With  the  constant  speed  motors  the 
counter  cone  is  driven  by  the  motor,  either  directly  or  by  belt,  and 
the  variations  in  spindle  speeds  are  obtained  in  the  usual  manner. 
In  the  variable  speed  motor  system,  the  motor  drives  the  spindle 
directly,  the  changes  in  speed  being  accomplished  by  changing  the 
speed  of  the  motor. 


CHAPTER  XXXIII. 

MISCELLANEOUS  SHOP  EQUIPMENT  AND  CONVENIENCES. 

The  use  of  compressed  air  in  the  shop  for  the  driving  of  small 
motors,  air  hammers,  drills,  hoists,  etc.,  is  quite  common.  Its 
convenience  and  adaptability  to  these  uses  more  than  balance  the 
losses  incident  to  its  compression.  Any  form  of  air-driven  tool 
or  motor  is  necessarily  an  extravagant  0ne  so  far  as  cost  per  horse 
power  developed  is  concerned. 

Many  of  these  motors  could  be  operated  by  steam,  but  the  heat 
would  prevent  them  from  being  conveniently  handled  and  the 
exhaust  must  be  piped  outside.  With  air,  on  the  other  hand,  the 
tool  or  motor  is  kept  cool  and  the  exhaust  discharges  in  the  room. 

One  of  the  most  important  uses  of  compressed  air  is  for  hoist- 
ing work.  In  Fig.  656  is  shown  a  pneumatic  hoist.  It  consists  of 
a  cylinder,  of  diameter  suitable  for  the  loads  it  has  to  lift,  in 
which  a  piston  having  a  cup  leather  packing  is  fitted.  The  piston 
rod  carries  a  hook  at  its  lower  end  for  receiving  the  connecting 
rope  or  chain  from  the  load.  The  compressed  air  is  piped  to  a  suit- 
able three-way  cock  which  admits  and  releases  it  from  under  the 
piston,  depending  on  which  way  the  cock  is  turned. 

In  its  action  the  air  hoist  is  much  quicker  than  the  chain  hoist. 
It  lifts  its  load  without  shock  or  jar,  and  is  generally  considered  as 
an  economical  method  of  lifting  material.  It  is  usually  attached 
to  a  crane  or  some  form  of  carrier,  as  it  is  in  most  cases  necessary 
to  pick  up  the  load  at  one  place  and  deposit  it  in  another.  If 
the  distance  carried  is  great,  the  hoist  is  uncoupled  after  the  load 
is  lifted,  the  air  in  the  cylinder  holding  it  up,  providing  the  cock 
and  rod  gland  do  not  leak.  This  avoids  a  very  long  connecting 
hose.  The  amount  of  air  required  to  make  a  lift  depends  on  the 
weight  raised,  the  full  tank  pressure  being  required  only  in  the 
case  of  a  maximum  lift.  A  considerable  amount  of  waste  usually 
occurs  in  the  filling  of  that  portion  of  the  cylinder  at  the  bottom 
which  does  not  represent  lift.  Thus,  if  the  piston  lifts  one  foot 
before  it  begins  to  raise  the  load,  that  volume  must  be  filled  witk 
air  at  the  required  pressure  before  any  useful  work  is  performed. 
It  is,  therefore,  always  best  to  couple  as  close  to  the  work  as  possi- 


5l8  MODERN    MACHINE    SHOP    TOOLS. 

ble  and  get  the  required  height  of  lift  in  the  lower  portion  of  the 
piston's  stroke. 

Hoists  of  the  class  shown  require  considerable  head  room. 
When  this  is  not  available  the  cylinder  may  be  placed  in  a  hori- 
zontal position,  as  shown  in  Fig.  657.  As  shown,  the  lift  is  made 
on  the  push  stroke,  and  the  method  of  coupling  gives  a  lift  double 
the  stroke  of  the  piston.  Short  cylinders  of  large  diameters  sus- 
pended as  shown  in.  Fig.  656  and  using  a  push  stroke  with  a  multi- 
plying gear,  are  frequently  used  in  places  where  head  room  is 
limited.  They  possess  the  advantage  of  not  taking  up  so  much 
room,  laterally,  as  the  form  shown  in  Fig.  657. 

Elevators  are  frequently  operated  by  pneumatic  hoists,  either 
by  direct  or  a  multiplied  lift. 

Pneumatic  hammers  for  chipping,  riveting,  and  calking  have 
come  into  very  general  use.  With  them  a  very  great  saving  in 
labor  is  effected,  as  one  hammer  in  the  hands  of  a  competent 
operator  will  perform  the  work  of  several  men  with  hand  tools. 

In  Fig.  658  is  illustrated  a  pneumatic  hammer  suitable  for 
medium  heavy  chipping  and  calking.  A  hose  connects  the  hollow 
handle  with  the  air  supply  and  the  valve  which  admits  the  air  to 
the  cylinder  is  controlled  with  the  thumb.  The  cylinder  contains 
the  piston  or  hammer  at  the  handle  end,  and  the  anvil  which  carries 
the  chisel  or  other  tool  at  the  nose  end.  The  pressure  of  the  air 
is  employed  in  giving  the  piston  a  rapid  reciprocating  motion,  it 
striking  with  full  force  on  the  anvil  at  each  forward  stroke  and 
cushioning  against  the  air  on  its  return  stroke.  These  hammers 
are  made  in  various  sizes,  suitable  for  all  classes  of  work.  The 
tool  shown  weighs  8  pounds  and  requires  25  cubic  feet  of  free  air 
per  minute  compressed  to  80  pounds  with  which  to  operate  it. 

The  pneumatic  drilling  machine  shown  in  Fig.  659  is  a  portable 
tool  much  used  for  drilling  and  reaming  on  boiler,  bridge  and 
structural  steel  work.  The  machine  shown  is  virtually  a  small, 
high  speed,  reciprocating  engine.  It  has  four  single  acting  cylin- 
ders with  nicely  fitted  trunk  pistons,  which  are  connected  with  a 
double  throw  crank,  carrying  at  its  lower  end  a  pinion  which 
meshes  with  a  gear  on  the  drill-carrying  spindle.  The  tool  shown 
weighs  30  pounds,  requires  35  cubic  feet  of  free  air  compressed  to 
80  pounds  per  minute  to  operate  it  and  wHl  drill  successfully  holes 
up  to  2*/2  inches  in  diameter.  Various  types  of  rotary  engines 
are  applied  to  this  class  of  machines.  They  are  not  as  economical 
in  air  consumption,  however,  as  the  piston  types. 


MISCELLANEOUS    SHOP    EQUIPMENT    AND    CONVENIENCES.    519 


FIG.  658. 


FIG.  659. 


FIG.  657. 


520 


MODERN    MACHINE    SHOP    TOOLS. 


Hand  hoists  are  much  used  in  the  handling  of  weights  too 
heavy  for  one  man  to  lift.  They  are  comparatively  slow  and  con- 
sequently not  well  adapted  to  regular  work  in  places  where  pneu- 
matic or  power  hoists  can  be  used.  They  are  more  of  the  nature 
of  a  jobbing  hoist,  are  compact,  portable  and  may  be  worked  in 
any  desired  position.  The  differential  hoist  shown  in  Fig.  660 
is  an  exceedingly  simple  single  chain  hoist.  The  two  upper 
sheaves  are  independent  of  each  other,  the  one  being  slightly 
larger  than  the  other.  By  pulling  the  chain  over  the  larger 
sheave  it  takes  up  faster  than  the  smaller  sheave  lets  out,  conse- 


FIG.  660. 


FIG.  66l. 


quently  the  hook  goes  up.  One  man  can  lift  from  800  to  1,000 
pounds  with  this  style  of  hoist. 

The  geared  hoist  Fig.  66 1  is  an  example  of  the  many 
hoists  of  this  character  that  are  made.  It  is  a  spur  geared  hoist 
with  a  suitable  brake  for  holding  the  load.  This  form  of  hoist 
is  more  rapid  than  those  using  a  worm  and  gear  and  is  compact, 
requiring  a  minimum  amount  of  head  room.  With  the  better 
hoists  of  this  class  one  man  can  lift  the  rated  load.  With  this 
class  of  hoist  the  higher  the  speed  the  less  the  weight  that  can 
be  raised  with  a  given  effort. 

Power  hack  sawing  machines,  an  example  of  which  is  shown 
in  Fig.  662,  have  come  into  very  general  use.  These  machines 


MISCELLANEOUS    SHOP    EQUIPMENT    AND    CONVENIENCES.     52! 

use  the  regular  pattern  of  hack  saw  blades,  which  with  proper 
care  will  do  a  remarkable  amount  of  cutting.  They  require  little 
attention  and  when  the  blades  are  properly  adjusted,  will  saw 
off  work  reasonably  square.  They  are  so  constructed  that  when 
the  blade  drops  through  the  work  the  machine  stops.  When  the 
blade  is  new  the  weight  holding  it  to  the  cut  should  not  be  too 


heavy,  as  the  cutting  teeth  are  sharp  and  bite  so  freely  that  there 
is  danger  of  stripping  off  the  teeth  or  breaking  the  blade,  especially 
if  the  work  is  of  small  diameter,  thus  permitting  contact  with  but 
a  few  teeth  at  each  point  in  the  stroke.  Tubing  is  very  hard  on 
blades  and  should  be  cut  with  light  pressure  and  saws  which  are 
somewhat  worn.  Oil  is  not  used  on  the  hack  saw  blade. 

In  Fig.  663  is  shown  a  "balancing  way"  used  in  the  balancing 


FIG.  663. 


522 


MODERN    MACHINE    SHOP    TOOLS. 


of-  rotating  parts,  as  pulleys,  spindles,  etc.,  which  from  the  nature 
of  their  work,  must  be  put  in  perfect  balance.  The  machine  has 
a  pair  of  smooth,  hardened  ways,  parallel  with  each  other,  and  so 
mounted  that  they  may  be  accurately  leveled.  Spindles,  or  work 
carried  on  spindles,  when  placed  on  the  ways  will  rotate  and  come 
to  rest  with  the  heavy  side  down.  By  removing  weight  from  the 
heavy  side  or  adding  to  the  light  side,  the  piece  may  be  brought 
into  perfect  balance  as  indicated  by  its  action  on  the  "way." 

For  tempering,  case-hardening,  brazing,  melting  of  babbitt, 
etc.,  a  gas  or  gasoline  forge  is  admirably  adapted.  They  are 
cleaner  and  more  convenient  than  coal  or  coke  fires.  With  the  gas 


FIG.  664. 


forge  a  supply  of  compressed  air  is  necessary.  With  the  gasoline 
forge,  an  example  of  which  is  sho«wn  in  Fig.  664,  an  air  pressure 
of  from  20  to  60  pounds  is  maintained  on  top  of  the  gasoline 
in  the  tank.  Two  or  more  burners  are  so  placed  that  their  blasts 
are  concentrated  at  a  common  point,  fire  brick  baffle  plates  re- 
taining the  heat. 

The  proper  lubrication  of  high  speed  machinery  requires  a 
liberal  supply  of  oil  and  consequently  some  means  of  catching 
this  oil  after  it  has  performed  its  work.  Self-oiling  boxes 
should  be  frequently  drained  of  old  oil  and  supplied  with  fresh. 


MISCELLANEOUS    SHOP    EQUIPMENT    AND    CONVENIENCES.    523 

The  oil  which  has  been  thus  used  is  unfit  to  be  used  again,  as 
it  is  full  of  impurities  which  have  been  washed  from  the  bear- 
ings. This  oil  usually  retains  all  of  its  lubricating  properties 
and  by  passing  it  through  a  suitable  filter  the  impurities  are  re- 
moved mechanically,  thus  cleansing,  refining  and  making  it  suit- 
able for  use  again. 

The  reclaiming  of  oil  which  cannot  be  drained  from  the  chips 
which  accumulate  in  the  pans  of  screw  machines,  or  other 
machines  using  oil  on  the  cutting  tools,  is  an  important  matter. 
This  class  of  oil  is  high  in  price  and  can  be  used  repeatedly  if 
reclaimed.  The  only  satisfactory  method  of  doing  this  is  by 


Fio.  665. 


means  of  a  centrifugal  separator,  an  example  of  which  is  shown 
in  Fig.  665.  In  this  machine  a  strong  inner  drum  mounted 
on  a  vertical  spindle  and  capable  of  high  rotation  is  filled  with 
the  oily  chips.  The  outer  casing  which  surrounds  the  drum 
serves  to  catch  the  oil  which  is  thrown  off  from  the  chips  by  the 
centrifugal  action.  In  this  manner  practically  all  of  the  oil  is 
reclaimed. 

The  accumulation  of  oily  waste  about  the  shop  is  a  constant 
source  of  danger  and  more  especially  in  cases  where  there  is  the 
possibility  of  its  receiving  moisture,  as  spontaneous  combustion 


524  MODERN    MACHINE    SHOP    TOOLS. 

is  very  apt  to  occur.  The  only  safe  way  to  dispose  of  this  ma- 
terial is  to  burn  it  at  regular  intervals.  While  accumulating  it 
should  be  thrown  in  iron  buckets  of  the  character  shown  in 
Fig.  666.  These  buckets  are  made  of  galvanized  iron  and  riveted 
together.  They  are  provided  with  legs  and  a  close  fitting  cover. 
In  case  the  waste  starts  to  burn  it  is  so  completely  cut  off  from 
the  air  that  the  combustion  is  necessarily  slow  and  may  be  de- 
tected by  the  smoke  and  odor. 

The  systematic  keeping  of  stock  and  tools  in  the  machine  shop 
is  a  matter  of  very  great  importance  and  one  requiring  for  each 
particular  case  a  great  deal  of  thought.  Small  tools,  jigs  and 


FIG.  666. 


FIG.  667. 


fixtures  should  be  kept  in  a  tool  room  under  the  charge  of  a  com- 
petent tool  v room  man  who  should  be  responsible  for  the  giving 
out,  receiving,  inspecting  and  repairing  of  all  tools  and  fixtures. 
The  tools  should  be  distributed  on  shelves,  racks  and  in  draw- 
ers in  such  a  manner  that  each  article  has  its  particular  place, 
thus  enabling  the  tool  man  to  select  it  upon  call  with  the  least 
possible  loss  of  time.  It  is  preferable  to  keep  tools  that  are  for 
general  use  about  the  shop  in  a  place  where  they  are  exposed 
to  view.  Tools  and  fixtures  of  a  special  character  may  be  kept 
in  drawers  properly  tagged.  In  the  case  of  jigs,  it  is  desirable 
to  keep  them  with  the  full  assortment  of  tools,  whether  stock  or 
special,  that  are  required  for  the  job,  in  separate  drawers.  The 


MISCELLANEOUS    SHOP    EQUIPMENT    AND    CONVENIENCES.     525 

operator  then  draws  all  that  he  requires  for  the  work  in  a  single 
lot  and  saves  the  time  and  chance  for  error  incident  to  drawing 
the  tools  separately. 

The  stock  room  is  an  extremely  important  feature  in  any 
well  organized  shop.  It  should  be  well  supplied  with  bins, 
shelves  and  racks  for  keeping  the  various  supplies  in  a  systematic 
manner,  and  it  should  be  in  charge  of  a  systematic  man. 

The  stock  room  should  receive  and  give  out  all  materials  and 
supplies,  keeping  at  all  times  an  exact  inventory  of  stock  on  hand. 

In  manufacturing  shops  all  stock  parts  which  go  to  make  up 
the  machine  or  articles  manufactured  are  kept  in  the  stock  room. 
This  gets  them  away  from  the  machine  as  soon  as  completed, 
and  puts  them  where  a  quantity  record  of  them  may  be  kept,  and 


FIG.  669. 


the  least  possible  amount  of  time  .lost  in  getting  them  when 
required  by  the  assembler. 

For  the  keeping  of  small  stock,  as  machine  screws,  cotters, 
taper  pins,  etc.,  revolving  racks  of  the  character  shown  in  Fig. 
667  are  admirably  adapted. 

Tools  and  work  racks  at  the  machines  are  very  convenient. 
In  Fig.  668  is  shown  an  excellent  form  of  lathe  rack  which  has 
two  shelves  for  work  and  tools,  with  a  drawer  for  the  mechanic's 
finer  tools.  A  similar  rack  of  larger  size  mounted  on  castors 
for  moving  from  machine  to  machine,  is  shown  in  Fig.  669. 
These  are  convenient  for  holding  work  that  is  to  be  operated 
upon  by  two  or  more  machines,  as  they  can  readily  be  moved  from 
one  to  another  without  the  necessity  of  rehandling  the  work. 
Racks  of  this  general  character  may  be  had  of  wood  or  metal  and 
of  forms  suitable  for  any  class  of  work. 


MODERN    MACHINE    SHOP    TOOLS. 


The  lathe  pan  shown  in  Fig.  670  is  intended  for  use  under 
the  lathe,  the  upper  tray  catching  the  chips  and  the  lower  one 
for  holding  work.  It  can  be  readily  rolled  from  under  the  ma- 
chine for  cleaning.  It  is  of  special  value  in  cases  where  an  oil 
or  water  cut  is  being  run  on  the  lathe,  as  it  catches  the  lubricant 


FIG.  670. 

which   can  be  drained   off  through  a    cock    provided    for    that 
purpose. 

In  Fig.  671  is  illustrated  a  form  of  pressed  steel  tote  box 
or  shop  pan.  They  may  be  had  in  a  large  variety  of  shapes  and 
sizes  and  are  admirably  adapted  to  the  holding  of  small  parts 


FIG.  671. 


and  supplies.     Small  hardwood  boxes  with  suitable  handles  are 
also  well  suited  to  this  purpose. 

When  an  oil  or  water  cut  is  occasionally  desirable  on  work 
in  the  lathe,  the  simple  device  shown  in  Fig.  672  serves  very 
nicely  and  is  much  more  convenient  than  the  makeshift  methods 
so  frequently  employed. 


MISCELLANEOUS    SHOP    EQUIPMENT    AND    CONVENIENCES. 

Large  cast  iron  plates  planed  smooth  and  true,  and  mounted 
on  suitable  legs,  are  very  convenient  for  the  laying  off  of  work. 


FIG.  672. 

They  should  be  kept  for  the  purpose  intended  and  not  allowed  to 
be  used  as  shelves  for  other  purposes. 


CHAPTER  XXXIV. 

% 

TABLES   AND    USEFUL  DATA. 

The  tables  and  data  contained  in  this  chapter  have  been 
selected  with  the  view  of  getting  together,  in  convenient  form, 
the  tabulated  information  to  which  the  mechanic  most  frequently 
wishes  to  refer. 

TABLE  OF  DIMENSIONS  OF  KEYS  AND  KEY-WAYS.— BAKER    BROS. 


Preferred 
Width  of 
Key-Way. 


Ne 
S 
Cu 


Prefe 
Thick 
of  K 


Nearest 
Fraotiona 
Thickness. 


1. 

1.062 

1.125 

1.187 

1.25 

1.312 

1.375 

1.437 

1.5 

1.562 

1.625 

1.687 

1.75 

1.812 

1.875 

1.937 

2. 

2.062 

2.125 

2.187 

2.25 

2.312 

2.375 

2.437 

2.5 

2.562 

2.625 

2.687 

2.75 

2.812 

2.875 

2.937 

3. 

3.125 

3.187 

3.25 

3.375 

3.437 

3.5 

3.625 

3.687 

3.75 

3.875 

3.937 

4. 


.25 

.265 

.281 

.296 

.312 

.328 

.343 

.359 

.375 

.39 

.406 

.421 

.437 

.453 

.468 

.484 

.5 

.515 

.531 

.547 

.563 

.578 


.641 

.656 

.672 

.687 

.703 

.719 

.734 

.75 

.781 

.797 

.812 

.844 

.a59 

.875 


.937 


.166 
.177 
.187" 
.198 
.208 
.219 


.25 

.26 

.271 

.281 

.292 

.302 

.312 

.323 

.333 

.344 

!364 
.375 


.406 

.416 

.427 

.437 

.448 

.458 

.469 

.479 

.49 

.5 

.521 

.531 

.542 

.562 

.573 

.583 

.604 

.614 

.625 

.646 

.«5»J 

.666 


.093 
.093 
.093 
.109 
.109 
.109 
.125 
.125 
.125 
.125 
.141 
.141 
.141 
.141 
1 
1 


1 

.171 

.218 

.218 

.218 

.218 

.218 

.218 

.218 

.218 

.25 

.25 

.25 

.25 

.25 

.25 

.312 

.312 

.312 

.312 

.312 

.312 

.343 

.343 

:.m 


.112 

.112 

.112 

.131 

.131 

.131 

,15 

,15 

,15 

.15 

.168 

.168 

.168 

.1(58 

.206 

.205 

.206 

.206 

.20tf 

.206 

.206 

.206 

.262 

.M2 

.2H2 

.2H2 

.S»i2 

.S2H2 

.2IJ2 

.262 

.3 

.3 

.3 

.3 

.3 

.3 

.375 

.375 

.375 

.375 

,375 

,375 

,412 

.412 

,412 


TABLES    AND    USEFUL   DATA. 


529 


TABLE  OP   DECIMAL  EQUIVALENTS  OF  8THS,   16THS,  32DS  AND  64THS  OP  AN  INCH. 


A  .015625 

H  .265625 

i|  .515635 

SI  .765625 

A   .03125 

3%   .28125 

££   .53125 

§|   .78125 

&  .046875 

il  .296875 

II  .546875 

Ii  .796875 

&     .0625 

A     .3125 

.5685 

52     .8125 

&  .078125 

ii  .328125 

II  .578125 

ii  .828125 

3»5   .09375 

Ji   .34375 

S?   .59375 

15   .84375 

/,  .109375 

SI  .359375 

II  .609375 

11  .859315 

|     .125 

|     .375 

I     .625 

I     .875 

B\  .140625 

IS  .390625 

Ii  .640625 

15  .890626 

3S5   .15625 

13   .40625 

15   .65625 

If   .90625 

H  .171875 

11  .421875 

||  .671875 

SI  .921875 

T\     .1875 

/„     .4375 

\l     .6875 

11     .9375 

i|  .203125 

If  .453125 

11  .703125 

li  .953125 

A   -21875 

H   .46875 

li   .71875 

gj   .96875 

H  .234375 

li  .484375 

IS  .734375 

II  .984375 

J     -25 

i     .5 

|     .75 

1     1. 

DIFFERENT  STANDARDS  POR  WIRE  GAUGE  IN  USE  IN  THE  UNITED  STATES. 

Dimensions  of  sizes  in  Decimal  Parts  of  an  Inch 


«i 

fi* 

§   1 

*6i 

i 

2 

^ 

0 

o  ** 

w  3 

ll 

HI 

fsj 

I'iffc" 

"S  a 

3  —  « 

II 

ll 

|2 

IfflJ 

?       3 

fag 

S  2 

ll 

II 

-**    — 

1*      ~fcj 

t>   O    ° 

^"*b^ 

X 

f-^5*"* 

*£ 

S3     M 

^S^ 

000000 

.464 

.46875 

000000 

.432 

.4375 

00000 

0000 

.46" 

.454 

.3938 

.400 

.40625 

0000 

000 

.40964 

.425 

.3625 

.372 

! 

.375 

000 

00 

.3648 

38 

.3310 

.348 

.34375 

00 

0 

.32486 

84 

.3065 

.324 

.3125 

0 

.2893 

.3 

.2830 

.300 

.227 

28125 

1 

2 

.25763 

.284 

.2625 

.276 

.219 

.265625 

2 

3 

.22942 

.259 

.2437 

.252 

.212 

.25 

3 

4 

.20431 

.238 

.2253 

.232 

.207 

.234375 

4 

5 

.18194 

22 

.2070 

.212 

.201 

.21875 

5 

6 

.16202 

203 

.19-^0 

.192 

201 

.203125 

6 

.14428 

.18 

.1770 

.176 

199 

.1875 

7 

8 

.12849 

.165 

.1620 

.160 

.197 

.171875 

8 

9 

.11443 

.148 

.1483 

.144 

.191 

.15625 

9 

10 

.10189 

.134 

.1350 

.128 

.191 

.140625 

10 

11 

.090742 

.12 

.1205 

.116 

.188 

.125 

11 

12 

.080808 

.109 

.1055 

.104 

.185 

.109375 

12 

13 

.071961 

.095 

.0915 

.092 

.182 

.09375 

13 

14 

.064084 

083 

.0800 

.080 

.180 

.078125 

14 

15 

.057068 

.072 

.0720 

.072 

.178 

.0703125 

15 

16 

.05082 

.065 

.0625 

.064 

.175 

.0625 

16 

17 

.045257 

.058 

.0540 

.056 

.172 

.05625 

17 

18 

.040303 

.049 

.0475 

.048 

.168 

.05 

18 

19 

.03589 

.042 

.0410 

.040 

.164 

.04375 

19 

80 

.081961 

.035 

.0348 

.036 

.161 

.0375 

20 

21 

.028462 

.032 

.03175 

.032 

.157 

.034375 

21 

22 

.025347 

.028 

.0286 

.028 

.155 

.03125 

22 

23 

.022571 

.025 

.0258 

.024 

.153 

.028125 

23 

24 

.0201 

.022 

.0230 

.022 

.151 

.025 

24 

25 

.0179 

.02 

.0204 

.020 

.148 

.021875 

25 

26 

.01594 

.018 

.0181 

.018 

.146 

.01875 

26 

27 

.014195 

016 

.0173 

.0164 

.143 

.0171875 

27 

28 

.012641 

.014 

.0162 

.0149 

.139 

.015625 

•28 

29 

.011257 

.013 

.0150 

.0136 

.134 

.0140625 

29 

30 
31 

.010025 
.008988 

.012 
.01 

.0140 
.0132 

.0124 
.0116 

.127 
.120 

.0125 
.0109375 

30 
31 

32 

.00795 

009 

.0128 

.0108 

.115 

.01015625 

32 

33 

.00708 

.008 

.0118 

.0100 

.112 

.009375 

33 

34 

.006304 

.007 

.0104 

.0092 

.110 

.00859375 

34 

35 

.005614 

.005 

.0095 

.0084 

.108 

.0078125 

35 

36 
37 

.005 

.004453 

004 

.0090 

.0070 
.0068 

.106 
103 

.00703125 
.006640625 

36 

37 

38 

.003965 

!.".".  . 

.0030 

101 

.00625 

38 

39 

003531 

.0052 

<99 

39 

40 

'(K  til  44 

..... 

.0048 

097 

40 

•UUUvft 

.... 

530 


MODERN    MACHINE    SHOP    TOOLS. 


CIRCUMFERENCE,  AREAS,  SQUARES,  ETC.,  OF  CIRCLES. 

Advancing  by  16ths,  8ths,  and  4ths.— 1  to  50. 


| 

-t-i 

I 

*l 

11 

<M 

<s 

uare. 

1 

•§ 

£ 

meter 
umber 

'1 

I 

i 

1 

2 

I 

.Sfc 

• 
3 

<! 

£ 

O 

1 

jB 

afc 

a 

•"1 

s 

O 

a 

$ 

*s 

5 

g 

3 
O 

flo 

I 

p 

o* 

CQ 

3 

1 

3.14 

.7854 

i. 

1. 

1. 

1. 

^y 

22.78 

41.28 

62.56 

381.08 

2.692 

1.935 

3.34 

.886 

1.13 

1.19 

1.031 

1.020 

IXt 

23.56 

44.18 

56.25 

421.88 

2.739 

1.967 

1^1 

3.53 

.994 

1.27 

1.42 

1.060 

1.040 

m 

24.35 

47.17 

W).06 

465.48 

2.784 

1.979 

1  ra 

3.73 

1.107 

1.41 

1.67 

1.0H9 

1.059 

8 

25.13 

50.26 

64 

612. 

2.828 

2 

1J4 

8.93 

1.227 

1.56 

1.95 

1.118 

1.077 

8J4 

25.93 

53.46 

68.06 

661.52 

2.872 

2'.021 

1  15 

4.12 

1.353 

1.73 

2.26 

1.146 

1.095 

8^6 

26.70 

5675 

72.15 

614.12 

2.915 

2.041 

4.32 

1.485 

1.89 

2.60 

1.173 

1.112 

f4 

2749 

60.13 

76.56 

669.92 

2958 

2.061 

1/8 

4.52 

1.623 

2.07 

2.97 

1.199 

1.129 

28.27 

63.62 

81. 

729. 

3. 

2.080 

•J1Z 

4.71 

1.767 

2.25 

3.38 

1.225 

1.145 

914 

29.06 

67.20 

85.56 

791.45 

3041 

2.098 

Il98 

4.91 

1.917 

2.44 

3.82 

1.250 

1.161 

91^ 

29.86 

70.88 

90.25 

857.37 

3.082 

2.118 

JSZ 

5.11 

2.074 

2.64 

4.29 

1.276 

1.176 

93^ 

30.63 

74.66 

95.06 

926.86 

3.1*2 

2.136 

lis 

5.30 

2.236 

2.85 

4.80 

1.299 

1.191 

10 

31.41 

78.54 

100 

1000 

3.162 

2.164 

1% 

5.50 

2.405 

3.06 

5.36 

1.323 

1.205 

11 

34.66 

95.03 

121 

1331 

3.317 

2.224 

I1! 

6.69 

2.580 

3.29 

5,95 

1.346 

1.219 

12 

37.69 

113.0 

144 

1728 

3.464 

2.289 

1% 

5.89 

2.761 

3.52 

6.69 

1.369 

1.233 

13 

40.84 

132.7 

169 

2197 

3.606 

2.351 

lie 

6.09 

2.948 

3.75 

7.27 

1392 

1.247 

14 

43.98 

1539 

196 

2744 

3.743 

2.410 

6.28 

3.142 

4. 

8. 

1.414 

1.260 

13 

47.12 

176.7 

226 

3375 

3.873 

2466 

jj  i 

6.48 

3.341 

4.25 

8.77 

1.436 

1.273 

16 

50.26 

201.0 

256 

40% 

4. 

2.620 

2V6 

6.68 

3547 

4.52 

9.59 

1.458 

1.286 

n 

53.40 

226.9 

289 

4913 

4.123 

2.571 

•2l3B 

6.87 

3.758 

4.78 

10.47 

1.479 

1.298 

18 

56.54 

254.4 

324 

5832 

4243 

2.621 

•gix 

7.07 

3.976 

5.06 

11.39 

15 

1.310 

19 

69.69 

283.5 

361 

6869 

4.359 

2.668 

2r5B 

7.26 

4.200 

6.35 

13.36 

1.621 

1.322 

20 

62.83 

314.1 

400 

8000 

4.472 

2.714 

2% 

7.46 

4.430 

5.64 

13.40 

1.541 

1.334 

21 

65.97 

346.3 

441 

9261 

4.583 

2.759 

2/B 

7.66 

4.666 

5.94 

14.48 

1.561 

1.346 

22 

69.11 

380.1 

484 

10648 

4.690 

2.802 

g  9 

7.85 

4.909 

6.25 

15.63 

1.581 

1.358 

23 

72-25 

415.4 

529 

12167 

4.796 

2844 

2^i 

8.05 

5.157 

6.57 

16.83 

1.600 

1.369 

24 

75.39 

452.3 

576 

13824 

4899 

2.885 

2^6 

8.25 

5.412 

6.89 

18.08 

1.620 

1.380 

2B 

78.54 

480.8 

625 

15625 

6. 

2.924 

2r| 

8.44 

5.673 

7.22 

19.41 

1.639 

1.391 

26 

81.68 

530.9 

676 

17576 

5.099 

2.963 

294 

8.64 

5.940 

7.56 

20.79 

1.668 

1.402 

27 

84.82 

572.6 

729 

19683 

6.196 

3. 

2  rl 

8.84 

6.213 

7.91 

22.25 

1.677 

1.412 

28 

87.96 

615.7 

784 

21952 

5.292 

3.037 

256 

9.03 

6.492 

8.27 

23.76 

1.695 

1.422 

29 

81.10 

6605 

841 

24389 

5.385 

3.072 

2i^ 

9.23 

6.777 

8.63 

2534 

1.714 

1.432 

30 

9424 

706.8 

900 

27000 

5.477 

3.107 

3 

9.42 

7.07 

9. 

27. 

1.732 

1.442 

31 

9759 

754.8 

961 

29791 

5.568 

3.141 

•3^6 

9.82 

7.67 

9.77 

30.52 

1.768 

1.462 

32 

100.5 

804.2 

1024 

32768 

5.657 

3.175 

3/4 

10.21 

8.30 

10.56 

34.33 

1.803 

1.482 

33 

103.7 

855.3 

1089 

35937 

5.745 

3.208 

•3% 

10.60 

8.95 

11.39 

38.44 

1.837 

1.6 

34 

106.8 

907.9 

1156 

39304 

5.831 

3.240 

3^2 

11.00 

9.62 

13.25 

42.88 

1.871 

1.518 

35 

110. 

962.1 

1225 

42875 

5916 

3.271 

3% 

11.39 

10.32 

13.14 

47.63 

1.904 

1.535 

36 

113.1 

1017.9 

1296 

46656 

6. 

3.302 

3% 

11.78 

11.05 

14.06 

62.73 

1.936 

1.563 

37 

116.2 

1075.2 

1369 

60663 

6.083 

3332 

3Js 

12.17 

11.79 

15.02 

58.17 

1.968 

1.570 

38 

119.4 

1134.1 

1444 

54872 

6164 

3.362 

4 

12.57 

12.57 

16. 

64. 

2. 

1.587 

39 

122.5 

1194.6 

1521 

59319 

6.345 

3.391 

4J4 

13.35 

14.19 

18.06 

76.78 

2061 

1.619 

40 

125.7 

1256.6 

1600 

64000 

6.325 

3.420 

4/^8 

14.14 

15.90 

20.25 

91.13 

2.121 

1.651 

41 

128.8 

1320.3 

1681 

68921 

6403 

3.448 

4M 

14.92 

17.72 

22.56 

107.16 

2.179 

1.681 

42 

131.9 

1385.4 

1764 

74088 

648' 

3.476 

5 

15.71 

19.63 

25. 

135. 

2.236 

1.710 

43 

135.1 

1452.2 

1849 

795U7 

6.557 

3.503 

16.49 

21.64 

27.56 

144.70 

2.291 

1.738 

44 

138.2 

1520.5 

1936 

85184 

6.633 

3.530 

•5/^3 

17.28 

33.76 

30.5J5 

166.37 

2.345 

1.765 

45 

141.4 

1590.4 

2025 

91125 

6.708 

3.657 

5% 

18.06 

25.97 

3306 

190.11 

2.398 

1.792 

46 

1445 

1661.9 

2116 

97336 

6.783 

3.583 

€ 

18.85 

38.29 

36 

216. 

2.449 

1.817 

47 

147.7 

1734.9 

2299 

103823 

6.856 

3.609 

614 

19.64 

60.68 

39.06 

244.14 

2.5 

1.832 

48 

150.8 

1809.6 

2304 

110592 

6.928 

3.634 

ti'-j 

20.42 

33.18 

42.26 

274.63 

2.550 

1.866 

49 

153.9 

1885.7 

2401 

117649 

7. 

3.659 

•6M 

21.21 

35.78 

45.56 

307.55 

2.599 

1.890 

50 

157.1 

1963.5 

2500 

125000 

7.071 

3.684 

7 

21.99 

38.48 

49. 

343. 

2.646 

1913 

NOTE.— To  find  the  4th  power  (or  biquadrate)  of  a  number,  multiply  the  square  by 
the  square. 

To  find  the  4th  root,  extract  the  square  root  twice  in  succession. 


TABLES    AND    USEFUL   DATA. 


531 


WEIGHTS  OP  SQUARE  AND  BOUND  BARS  OP  WROUGHT  IRON  IN  POUNDS  PER 
LINEAL  FOOT.— KENT. 

Iron  weighing  480  Ibs  per  cubic  foot.    For  steel  add  2  per  cent. 


Thickness 
or 
Diameter 
in  Inches. 

Weight  of 
Square  Bar 
One  Foot 
Long. 

Weight  of 
Round  Bar 
One  Foot 
Long. 

Thickness 
or 
Diameter 
in  Inches. 

Weight  of 
Square  Bar 
One  Foot 
Long. 

Weight  of 
Hound  Bar 
One  Foot 
Long. 

A 

.013 

.010 

*i« 

55.01 

43.21 

L/C 

.0-J2 

.041 

4V6 

56.72 

44.55 

3 

.117 

.092 

4'iff 

68.45 

45.91 

IX 

.208 

.164 

4J4 

60.21 

47.29 

IB« 

.326 
.469 

.256 
.368 

8 

61.99 
63.80 

48.69 
60.11 

7 

.638 

.501 

4  7 

65.64 

51.55 

1^ 

.833 

.654 

4Jy| 

67.50 

53.01 

9 

1.055 

.828 

4i9e 

69.39 

54.50 

RZ 

1.023 

496 

71.30 

56.00 

11 

L576 

1.237 

4 

7324 

57.52 

94 

1.875 

1.473 

494. 

75.21 

59.07 

I 

2.201 
2.552 

1.728 
2.004 

ill 

77.20 
79.22 

60.63 
62.22 

is 

1 

2.930 

2.301 

4*1 

81.26 

63.82     • 

3.333 

2618 

5 

83.33 

6545 

l 

3.763 

2.955 

5A 

85.43 

67.10 

IZ 

4.219 

3.313 

§L£ 

87.55 

68.76 

I36 

4.701 

3.692 

5i3s 

89.70 

70.45 

IX 

6.208 

4.091 

5>4 

91.88 

72.16 

I 

6.742 

4.510 

55 

94.08 

73.89 

8 

6.302 

4.950 

5% 

96.30 

75.64 

7 

6.888 

5.410 

5r7ff 

98.55 

77.40 

il 

7.500 

5,890 

5/^j 

1008 

79.19 

9 

8.138 

6.392 

5r96 

103.1 

81.00 

RZ 

8.802 

6.913 

5^6 

105.5 

82-83 

IS 

9.492 

7.455 

5l5 

107.8 

84.69 

3^ 

10.21 

8.018 

594 

110.2 

86.56 

13 

10.95 

8.601 

gi| 

1126 

88.45 

ill 

11.72 

9.204 

57^ 

115.1 

90.36 

He 

12.51 

9828 

511 

117.5 

92.29 

2 

13.33 

10.47 

6 

1200 

94.25 

14.18 

11.14 

125.1 

98.22 

2V6 

lo.OS 
15.95 

11.82 
12.53 

i 

130.2 
135.5 

102.3 
106.4 

2^| 

16.88 

13.25 

•8 

140.8 

110.6 

2  5 

17.83 

14.00 

6^ 

146.3 

1149 

2% 

1880 

14.77 

6M 

151.9 

119.3 

2l76 

1980 

15.55 

6j| 

157.6 

123.7 

2^6 

2083 

16.36 

1 

1633 

128.3 

2j9e 

21.89 

17.19 

7j^ 

169.2 

1329 

•246 

22.97 

18.04 

7J4 

1752 

137.6 

211 

24.08 

18.91 

7*2 

181.3 

142.4 

294 

25.21 

19.80 

7V« 

187.5 

147.3 

2li 

26.37 

20,71 

79s 

193.8 

ir>2.2 

2?6 

27.55 

21.64 

794 

200.2 

157.2 

2J1 

28.76 

22.59 

7% 

2067 

162.4 

3 

30.00 

2356 

8 

213.3 

167.6 

31.26 

24.58 

226.9 

178.2 

3^6 

32.65 

25.57 

oiy 

240.8 

189.2 

3  3 

33.87 

26.60 

814 

255.2 

2004 

gix 

35.21 

27.65 

9 

270.0 

212.1 

3is 

36.58 

.       2873 

2852 

224.0 

3% 

37.97 

29.82 

9^1 

3-0.8 

236.3 

3  7 

39.39 

3094 

994 

3169 

348.9 

3!^ 

4083 

32.07 

10 

3333 

261.8 

3r9 

4230 

3323 

10J4 

350.2 

275.1 

3% 

43.80 

3440 

10i6 

367.5 

2886 

sTI 

45.33 

3560 

1094 

385.2 

302.5 

394 

46.88 

36.82 

11 

403.3 

316.8 

313 

48.45 

38.05 

11J4 

421.9 

331.3 

3% 

5005 

39.31 

llij 

4408 

346.2 

3 

51  68 

40.59 

1194 

4602 

361.4 

4 

63.33 

41.89 

12 

480. 

377. 

MODERN    MACHINE    SHOP    TOOLS. 


WEIGHT  OF  FLAT  BAR  IRON. 


J, 

THICKNESS   IN    INCHES. 

fl 

,-« 

tf 

A 

M 

A 

K 

A 

H 

N 

* 

« 

1 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

JX 

.11 

.21 

.31 

.42 

.62 

.63 

.73 

.84 

% 

.13 

.26 

.40 

.53 

.66 

.79 

.92 

1  (16 

1.32 

0 

16 

32 

.47 

.63 

.79 

.95 

1.11 

138 

1.58 

1.89 

fcg 

.18 

.37 

.55 

.74 

.92 

1.11 

1.29 

1.48 

1.85 

2.22 

2.58 

1 

.21 

.42 

63 

.84 

1.05 

1.26 

1.47 

1.68 

2.11 

2.53 

2.95 

3.37 

jy 

.24 

*47 

.71 

.95 

1.18 

1.42 

1.66 

1.90 

2.37 

2.84 

3.33 

3.79 

V 

26 

53 

79 

1.05 

1.32 

1.58 

1.84 

2.11 

2.63 

3.16 

3.68 

4.21 

i 

.29 
.32 
.34 
37 

.58 
.63 
.68 
.74 

.87 
.95 
1.03 
1.11 

1.16 
126 
1.37 
1.47 

1.45 
1.58 
1.71 
1.84 

1.74 
1.90 
2.05 

2.21 

2.03 
2.21 
2.39 

2.58 

2.33 
2.53 
2.74 
2.95 

2.89 
8.16 
3.42 
3.68 

3.47 
3.79 
4.11 
4.42 

4.05 
4.42 
4.79 
5.16 

4.63 
5.05 
5.47 

5.89 

?l 

.40 
42 

.79 
84 

1.18 
1.26 

1.58 

1.68 

1.97 
2.11 

2.37 
2.53 

2.76 
2.95 

3.16 
3.37 

3.95 
4.21 

4.74 
5.05 

5.53 

5.89 

6.32 
6.74 

| 

.45 
.47 
.50 
.53 
55 

.90 
.95 
1.00 
1.05 
1  11 

1.34 
1.42 
1.50 
1.58 
1.66 

1.79 
1.90 
2.00 
2.11 
2.21 

2.24 
2.37 
2.50 
2.63 
2.76 

2.68 
2.84 
3.00 
3.16 
3.32 

3.13 
3.32 
3.50 
3.68 

387 

3.58 
3.79 
4.00 
4.21 
4.43 

4.47 
4.74 
5.00 
5.26 
553 

5.37 
5.68 
6.00 
6.32 
6.63 

6.26 
6.83 
7.00 
7.37 

7.74 

7.16 

7.58 
8.00 
8.42 
8.84 

3 
4  4 

.58 
.61 
.63 
.68 
.74 
.79 
84 

1.16 
1.31 
1.26 
1.37 
1.47 
1.58 
1  68 

1.74 
183 
1.90 
3.05 
3.21 
3.37 
2.53 

2.32 
2.42 
2.53 
2.74 
295 
3.16 
3.37 

2.89 
3.03 
3.16 
3.42 
3.68 
3.95 
4.21 

3.47 
363 
3.79 
411 
4.42 
4.74 
5.05 

4.05 
4.24 
442 
4.79 
5.16 
5.53 
5.89 

4.63 
4.84 
5.05 
5.47 
5.89 
6.32 
6.74 

5.79 
6.05 
6.32 
6.84 
7-37 
7.89 
8.42 

6.95 
7.26 

7.58 
8.21 
8.84 
9.47 
10.10 

8.10 
8.47 
8.84 
9.58 
10.32 
11.05 
11.79 

9.26 
9.68 
10.10 
10.95 
11.79 
12.63 
13.47 

5  4 

.90 
.95 
1.00 
1.05 

1.79 
1.90 
2.00 
2.11 

2.68 
2.84 
3.00 
3.16 

3.58 
379 
4.00 
4.21 

4.47 
4.74 
5.00 
5.26 

5.37 
5.68 
6.00 
6.32 

6.26 
663 
7.00 
7.37 

7.16 

7.58 
8.00 
8.42 

8.95 
9.47 
10.00 
10.53 

10.74 
11.38 
12.00 
12.63 

12.53 
13.26 
14.00 
14.74 

14.31 
15.16 
16.00 
16.84 

1  11 

3.32 

4.42 

5.53 

6.63 

7.74 

8.84 

11.05 

13.26 

15.47 

17.68 

1 

1.16 
1.21 
1.26 

2'.32 
3.43 
3.53 

3.47 
3.63 
3.79 

4.63 

484 
5.05 

5.79 
6.05 
6.32 

6.95 
7.26 
7.58 

8.10 

8.47 
8.84 

9.26 
9.68 
10.10 

11.58 
12.10 
12.63 

13.89 
14.53 
15.16 

16.21 
16.95 
17.68 

18.52 

19.37 
20.21 

PLATE  IRON. 

WEIGHT  OF  SUPERFICIAL*    FOOT. 


Thickness  in  inches. 

Weight,  Ibs. 

Thickness  in  inches. 

Weight,  Ibs. 

Is  =  .03125 
f  =  .0625 
-   0937 

1.25 
2.519 

3.788 

?s  =    .3125 
%=    .375 
i7«  =    .4375 

12.58 
15.10 
17.65 

-   125 

5.054 

}4  —       5 

20.20 

™  -   1562 

6.305 

&  =    .5625 

22.76 

&  -  .1875 

7.578 

%=    .625 

25.16 

372  -   2187 

8.19 

%=    .75 

30.20 

M  —  25 

1009 

%  =    .875 

35.30 

£  =  ]2812 

11.38 

1     =  1. 

40.40 

TABLES    AND    USEFUL   DATA. 


533 


SPBCIFIC  GRAVITY  AND  WEIGHT  OF  VARIOUS  METALS. 


METAL. 


Specific 
Gravity. 


Aluminum,  cast 2.fi60 

wrought 2.670 

Antimony 6.712 

Brass,  Sheet,  Copper  75.  Zinc  25 8.450 

"     Yellow,  Copper  66,  Zinc  34 8.300 

"     Plate 8.380 

"     Cast 8.IOU 

"     Wire 8.214 

Bronze,  Gun  Metal 8.750 

Copper  84,  Tin  16 8832 

Copper  81,  Tin  ) 9 8.700 

Phosphor— Bearing- Meta      9.214 

Copper,  cast... 8.788 

plates 8.6f8 

wire  and  bolts , 8  8fcO 

Gold,pure,  cast 19.258 

"     hammered 19.361 

"     22caratstine 17.486 

"     20  carats  fine 15.109 

Iridium,  hammered 23.000 

Iron,  cast,  gun  metal 7.308 

k     ordinary,  mean 7.207 

wrought  bars 7.788 

wrought  wire         —   7.774 

"     wrought  rolled  plates  .   7.704 

Lead,  cast 11.352 

-      rolled    11.388 

Mercury— 40  deg 15.632 

+32deg ...  13.598 

-f60deg 13.569 

212deg 13.370 

Nickel.  ...   8800 

"      cast 8.279 

Platinum,  hammered 20.337 

native 16.000 

rolled 22.069 

Rpd  Lead 8.940 

Silver,  pure,  cast 10.474 

hammered 10.511 

Steel,  tempered  and  hardened 7.818 

"     plates 7.806 

"     crucible 7.842 

"     Bessemer 7852 

Tin,  Corniah,  hammered 7.390 

pure 7.291 

.Zinc,  cast 6.861 

"     rolled..  7.191 


Weight  of  a 

Cubic  Inch 

in  Lbs. 


.0926 
.0906 
.2428 
.3056 
.2997 


.2972 
.3165 
.3194 
.2929 
.3332 
.3179 
.3146 
.3212 
.6965 
.7003 
.6325 


.8319 

.264 

.2607 

.2817 

.2811 

.^787 

.4106 

.4119 

.5661 

.4918 

.4908 

.4836 

.3183 

.2994 

.7356 

.5787 

.7982 

.324 

.3788 

.3802 

.2828 

.2823 

.2836 

.284 

.2673 

.2637 

.2482 

.26 


Weight  of  a 

Cubic  Foot 

in  Lbs. 


160. 

156.5 

419.5 

528. 

517.9 

522.9 

506.3 

513.5 

546.9 

5519 

506.1 

575.8 

647.2 

543.7 

555.1 

1204. 

1210. 

1093. 
981.8 

1437. 
456.2 
450.4 
486.8 
485.8 
481.6 
709.5 
711.7 
978.8 
849.8 
848.1 
835.7 
550. 
517.4 

1271. 


1379. 
559.9 
654.6 
657. 
488.7 
487.7 
490.1 
490.7 
461.9 
455.7 
428.8 
449.4 


WEIGHT  OP  VARIOUS  SUBSTANCES.— RICHARDS. 


Name  of  Substance. 


Weight  of 

1  Cubic  Foot 

in  Lbs. 


Name  of  Substance. 


Weight  of 

1  Cubic  Fool 

in  Lbs. 


Brickwork 

Clay 

Coal 

Coke 

Earth,  Loose, 

Earth,  Hammed 

Granite 

Sandstone 

Water,  Fresh 

Water.  Salt      

Alcohol 


100  to  120 

120  to  130 

80  to    82 

45  to    62 

76  to    90 

100  to  120 

160  to  165 

135  to  150 

62.3  to  62.5 

63  to  65 

50  to  60 


Oils,  various 

Acid,  Sulphuric. 

Oak  Wood 

Pmc,  White 

Pine,  Yellow..  . 

Air 

Steam 

Snow 

Coal  Gas .  

Carbonic  Acid... 


54  to  57 

114  to  116 

42  to  53 

27  to  30 

a5  to  45 

.08  to  .080 

.05  to  .055 

5  2  to  5.5 

.035  to  .036 

.122  to  .123 


534 


MODERN    MACHINE    SHOP    TOOLS. 


WEIGHT  OP  CASTINGS  FROM  PATTERNS. 

Simpson  Bolland. 


A  Pattern 
Weighing  One  Pound, 
Made  of— 

Will  Weigh  when  Cast  in 

Cast  Iron. 

Zinc. 

Copper. 

Yellow 
Brass. 

Gun 
Mefal. 

Mahogany  —  Nassau  

Lbs. 
10.7 
12.9 
8.5 
12.5 
16.7 
14.1 
9. 

Lbs. 
10.4 
12.7 
8.2 
12.1 
16.1 
13.6 
8.6 

Lbs. 
32.8 
15.3 
10.1 
14.9 
19.8 
16.7 
10.4 

Lbs. 
12.2 
14.6 
9.7 
14.2 
19. 
16. 
10.1 

Lbs. 
12.5 
15. 
9.9 
14.6 
19.5 
16.5 
10.9 

Honduras..  .  . 
Spanish  
Pine  -Red  .... 

White  

"       Yellow  .. 

Oak  

UNITS  OF  HEAT  IN  ONE  POUND  OF  FUELS. 


Anthracite 14,500 

Bituminous 14,000 

Petroleum,  light 22,600 

Petroleum,  heavy 19,440 


Petroleum,  refined. 
Petroleum,  crude.. 

Coal  Gas 

Water  Gas  .. 


19,26O 
19,210 
20,200 
8,500 


TABLE  OF  RELATIVE  VALUE  OF  NON-CONDUCTORS. 

Chas.  E.  Emery. 


Non-Conduct  or. 

Value. 

Non-Conductor. 

Value. 

Wood  Felt 

1000 

550 

Mineral  Wool  No.  2          

.832 

Slaked  Lime 

480 

Mineral  \V  ool  with  Tar  

715 

Gas  House  Carbon 

470 

Sawdust...     ;..., 

.680 

Asbestos 

363 

Mineral  Wool  No.  1  

.676 

Coal  Ashes    . 

345 

Charcoal    ....      

632 

Coke  in  lumps 

277 

Pine  Wood,  across  fiber  

.553 

Air  space  undivided 

136 

PROPERTIES  OF  METALS.— RICHARDS. 


Names  of  materials. 

Weight  in 
Ibs.  of  a 
cubic  foot. 

Weight  in 
Ibs.  of  a 
cubic  inch. 

Relative 
Weight. 
Water,  1,000 

Tensile 
strength 
Ibs.  per  in. 
section 

Melting 
point  in 
degrees 
Fahrenheit. 

Wrought  iron,  avge. 

485.0 

.277 

7,700 

56,000 

3,000 

Cast  iron. 

450.0 

.260 

7,200 

16,000 

2,300 

Cast  steel, 
Bessemer  steel,   " 

487.0 
489.0 

.280 
.280 

7,800 
7,852 

100,000 
90,01:0 

2,500 
2,500 

Cofrper, 

547.0 

.316 

8,780 

33,000 

3,0('0 

Brass,                   ** 

500.0 

.381 

8,100 

20,000 

1,800 

Tin, 

455.0 

.210 

7.290 

5,dOO 

446 

Lead, 

709.0 

.410 

11,352 

2,000 

600 

Silver, 

653.0 

.378 

10,474 

30,000 

1,801-) 

•-M.OJOS  jo 
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jo  'ox 


TABLES    AND    USEFUL   DATA.  535 

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536 


MODERN    MACHINE    SHOP    TOOLS. 


TABLES    AND    USEFUL   DATA. 


537 


TABLE  OP  EMERY   WHEEL  SPEEDS. 


Diam.  Whee'. 

Rev.  per  Minute 
for 
Surface  Speed 
of  4,000  Feet. 

Rev.  per  Minute 
for 
Surface  Speed 
of  5,000  Feet. 

Rev.  per  Minute 
for 
Surface  Speed 
of  6,000  Feet. 

1  inch. 

15,279 

19,099 

2?,918 

Q            " 

7,639 

9,549 

11,459 

3     •* 

5,093 

6,366 

7,639 

4      " 

3,830 

4,775 

5.730 

5      " 
6      " 

3,056 
3,546 

3,820 
3,183 

4,584 

:5>20 

7 

2,183 

2,728 

TU'74 

8      " 

1,910 

2,387 

2,865 

10      " 

1,528 

1,910 

2,298 

12      " 

1,273 

1,592 

1,910 

14      " 

1,091 

1,364 

1,637 

16      " 

955 

1.194 

1,432 

18      " 

849 

1,061 

1,273 

20     " 

'       764 

955 

1,146 

82      ** 

694 

868 

1,042 

24      " 

637 

796 

955 

26      " 

586 

7:« 

879 

28      •* 

546 

683 

819 

.30      " 

509 

637 

764 

o2      " 

477 

596 

716 

34      '| 

449 

561 

674 

96 

424 

531 

637 

38     " 

402 

503 

603 

40      " 

382 

478 

573 

42      " 

364 

455 

548 

44      " 

347 

434 

521 

46      " 

332 

415 

498 

48      •' 

318 

397 

477 

50      " 

306 

383 

459 

52      " 

294 

369 

441 

54      " 

283 

354 

426 

56      u 

273 

341 

410 

58      " 

264 

330 

396 

«y    " 

255 

319 

383 

THE     SPEED      OP     DRILLS. 

Cleveland  Twist  Drill  Co. 


Diam. 
of 
Drill. 

Speed 
for  Soft 
Steel. 

Speed 
for 
Iron. 

Speed 
for 
Brass. 

Diam. 
of 
Drill. 

Speed 
for  Soft 
Steel. 

Speed 
for 
Iron. 

Speed 
for 
Brass. 

16 

1,824 

2,128 

3,648 

» 

108 

125 

215 

912 

1,064 

1.824 

V£ 

102 

118 

203 

3 

608 

710 

1.216 

3 

96 

112 

192 

H 

456 

533 

912 

M 

91 

106 

182 

A 

365 

425 

730 

* 

87 

101 

174 

•LA 

304 

355 

608 

$6 

83 

97 

165 

n 

260 

304 

520 

T?tf 

80 

93 

159 

& 

228 

266 

456 

76 

89 

152 

ft 

203 
182 

236 
213 

405 

365 

ft 

73 
70 

85 
82 

145 
140 

11 

166 

194 

332 

n 

68 

79 

135 

94 

153 

177 

304 

K 

65 

'•6 

130 

140 

164 

280 

12 

63 

73 

125 

130 

162 

260 

/fa 

60 

71 

122 

122 

142 

243 

is 

59 

69 

118 

1 

114 

133 

228 

2 

57 

67 

114 

53« 


MODERN    MACHINE    SHOP    TOOLS. 


TABLE  OF  SIZES  OF  TAP  DRILLS. 


Tap  Diameter. 

Threads  per  Inch. 

Drill  for  V  Thread. 

Drill  for 
U.  S.  Standard. 

H 

16 

18 

20 

352                     3S2               ii 

, 

392 

16 

18 

20 

T3S         ii       ii 

y5fi 

16 

18 

372                   ii 

J4 

ti 

16 

18 

H          H 

Jl 

14 

16 

18 

J4                     392               3% 

392 

32 

14 

16 

18 

if          Ii        ii 

16 

14 

16 

Ii                      3* 

32 

u 

14 

16 

if          % 

y 

12 

13 

14 

%          11       ii 

H 

12 

14 

'  T7*          11 

/e 

N 

10 

11 

12 

3a       H       « 

M 

16 

11 

12 

re              r9« 

3/ 

10 

11 

12 

If         H      % 

K 

H 

10 

•  ' 

^ 

9 

10 

If32        §i 

R 

11 

9 

II 

1 

8 

\l 

m 

TAP  DRILL  SIZES. 

For  Gas  Taps. 


Diameter  of  Tap  or 
Size  of  Pipe. 

Diameter  of  Drill. 

Diameter  of  Tap  or 
Size  of  Pipe. 

Diameter  of  Drill. 

\b  inch 
1  4 

2  It  inch 

i;»i  • 

1J4  inch 

N 

3^    " 

\\\  inch 

3"  :: 

att*  " 

MACHINE    SCREW  TABLE. 


Screw  Gauge 
Size. 

Diameter  in 
Decimals. 

Appi-oximate 
Diameter. 

No.  Threads 
per  Inch. 

Size  of 
Tap  Drill. 

2 

.0842 

A 

M 

49 

3 

.0973 

A 

48 

45 

4 

.1105 

•9 

36 

42 

5 

.1236 

^ 

36 

38 

6 

.1368 

e9* 

32 

35 

7 

.1500 

& 

32 

30 

8 

.1631 

A 

32 

29 

9 

.1763 

H 

30 

27 

10 

.1894 

TU 

24 

25 

11 

.2026 

^ 

24 

21 

12 

.2158 

372 

24 

17 

13 

.2289 

££ 

22 

15 

14 

.2421 

tt 

20 

13 

15 

.2552 

y* 

20 

8 

16 

.2684 

ii 

18 

6 

17 

.2816 

32 

18 

2 

18       . 

.2947 

Jl 

18 

1 

19 

.3079 

TB 

18 

C 

20 

.3210 

Ii 

16 

D 

22 

.3474 

y 

16 

J 

24 

.3737 

% 

16 

N 

26 

.4000 

'  Ji 

16 

P 

28 

.4263 

§i 

14 

R 

30 

.4526 

§49 

14 

U 

TABLES    AND    USEFUL   DATA. 


539* 


TRANSMISSION  OF  POWER  BY  LEATHER  BELTING. 

Single  Leather. 


'    Belt  Speed. 

600 

1200 

1800 

2400 

3000 

3600 

4200 

4800 

5400 

6000 

Width  of  Belt. 

H  P 

H  P 

H  P 

H  P 

H  P 

H  P 

H  P 

HP 

H  P 

H  P 

1  in... 

1 

2 

3 

4 

5 

Q 

7 

8 

g 

2  in        .         .... 

2 

4 

g 

8 

10 

12 

14 

16 

18 

•'ii 

;j  in  

3 

6 

9 

12 

15 

18 

*1 

24 

27 

30 

4  in.        .           ..... 

4 

8 

12 

16 

20 

24 

28 

33 

36 

40 

5  in  

5 

10 

15 

20 

25 

30 

35 

40 

45 

fid 

6 

12 

18 

24 

30 

36 

42 

48 

54 

n 

8  in.              ... 

8 

16 

24 

32 

40 

48 

56 

64 

72 

80 

9  in 

9 

18 

27 

36 

45 

54 

63 

72 

81 

00 

10  in... 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

12  in 

12 

24 

36 

48 

60 

72 

84 

96 

108 

120 

14  in  

14 

28 

42 

56 

70 

84 

98 

112 

126 

140 

16  in.  .  . 

16 

32 

48 

64 

80 

96 

112 

128 

144 

160 

Double  Leather. 


Belt  Speed. 

4GO 

800 

1200 

1600 

2000 

2400 

2800 

3200 

36CO 

4000 

5000 

Width  of  Belt. 

H  P 

H  P 

H  P 

H  P 

H  P 

H  P 

H  P 

HP 

H  P 

H  P 

H  P 

4  in 

4 

8 

12 

16 

20 

24 

28 

32 

36 

40 

50 

6  in.. 

6 

12 

18 

24 

30 

36 

42 

48 

54 

60 

75 

8  in.  .. 
10  in 

8 
10 

16 

20 

24 
30 

32 
40 

40 
50 

48 
60 

56 
70 

64 

80 

72 

90 

80 
100 

100 

125 

12  in  

32 

24 

36 

48 

60 

72 

84 

96 

108 

130 

150 

16  in 

16 

32 

48 

64 

80 

96 

112 

128 

144 

160 

200 

20  in 

20 

40 

60 

80 

100 

120 

140 

160 

180 

200 

250 

24  in 

24 

48 

72 

96 

120 

144 

168 

192 

216 

240 

300 

30  in 

30 

60 

90 

120 

150 

180 

210 

240 

270 

300 

330 

36  in  

36 

72 

108 

144 

180 

216 

252 

288 

334 

370 

450 

40  n 

40 

80 

120 

160 

200 

240 

280 

320 

360 

400 

500 

ROPE  DRIVING. 
TABLE  OF  THE  HORSE  POWER  OF  TRANSMISSION  ROPE  BY  O.  W.  HUNT. 

The  working  strain  is  800  Ibs.  for  a  2-inch  diameter  rope  and  is  the  same  at  all 
speeds,  due  allowance  having  been  made  for  loss  by  centrifugal  force. 


Diameter 
Rope. 

Speed  of  the  Rope  in  Feet  per  Minute. 

Smallest 
Diameter 
Pulleys. 

1COO 

2000 

2500 

3000 

35CO 

4000 

4500 

5000 

6000 

7000 

:14  in 

3.3 
4.5 
5  8 
9.2 
13  1 
18  0 
23.1 

4.3 
5.9 
7.7 
12.1 
17.4 
23  7 
30.8 

6  2 

7.0 
92 
14  3 
20.7 

28.2 
36.8 

5.8 
8.2 
10.7 
16  8 
23.1 
32  8 
43.8 

6.7 
9  1 
11  9 
18  6 
26.8 
36  4 
47.6 

7.2 
9  8 
12  8 
20.0 
28.8 
39  2 
51  2 

7.7 
10.8 
13.6 
21  2 
30  6 
41  5 
54  4 

7.7 
10.8 
13.7 
21.4 
30.8 
41.8 
54.8 

7.1 
9.3 

12  5 
19.5 
28.2 
37  4 
500 

4.9 
6.9 
8.8 
13.8 

35^2 

30  in. 
36  in. 
42  in. 
54  in. 
60  in. 
72  in. 
84  in. 

1      in. 
1J4  in  
1^  in.  
194  in  
2     in  

540 


MODERN    MACHINE    SHOP    TOOLS. 


TRANSMITTING  EFFICIENCY  OF  TURNED  IRON  SHAFTING  AT  DIFFERENT  SPEEDS. 

As  Prime  Mover  or  Head  Shaft  carrying  Main  Driving-  Pulley 
or  Gear,  well  supported  by  bearings. 


Diameter 
of  Shaft. 

Number  of  Revolutions  per  Minute. 

60 

80 

ICO 

125 

150 

175 

200 

225 

250 

275 

300 

1%  in         

H  P 

2.6 
3.8 
5.4 

H  P 

3.4 
6  1 
7.3 
10 
13 
17 
22 

33 
41 

58 
80 

H  P 

4.3 
6.4 
8.1 
12.5 
16 
20 
27 
34 
42 
51 
72 
100 

H  P 

5.4 
8 
10 
15 
20 
25 
34 
42 
52 
64 
90 
125 

H  P 

6.4 
9.6 
12 
18 
24 
30 
40 
51 
63 
76 
108 
150 

H  P 

7.5 
11.2 
14 
22 
28 
35 
47 
59 
73 
89 
126 
175 

H  P 

8.6 
12.8 
16 
25 
32 
40 
54 
68 
84 
102 
144 
200 

H  P 

9.7 
14.4 
18 
28 
36 
45 
61 
76 
94 
115 
162 
2^5 

HP 

10.7 
16 
20 
31 
40 
50 
67 
85 
105 
127 
180 
250 

H  P 

11.8 
17.6 
22 
34 
44 
55 
74 
93 
115 
140 
198 
275 

H  P 

1-2.9 
19.3 
24 
37 

48 
60 
81 
102 
126 
153 
216 
300 

2     in 

5ki  in 

7.5 
10 

13 
16 
20 
25 
3(1 
43 
60 

2%  in 

3      in  
314  in  ,  

3M  in 

4      in.  

5      in  

TRANSMITTING  EFFICIENCY  OF  TURNED  IRON  SHAFTING  AT  DIFFERENT  SPEEDS. 

As  Second  Movers  or  Line  Shafting.    Bearings  8  Feet  Apart. 


Number  of  Revolutions  per  Minute. 


Diameter  of  Shaft. 

100 

125 

150 

175 

200 

225 

250 

275 

300 

325 

850 

Inches. 

H.  P. 

H.  P. 

H.P 

H.P. 

FT.  P. 

H.P. 

H.P. 

H  P. 

H.P. 

H.P. 

H.P. 

6 

7.4 

8.9 

10.4 

11.9 

13.4 

14.9 

16.4 

17.9 

19.4 

*0.9 

]7£ 

7.3 

9.1 

109 

12.7 

145 

16.3 

18.2 

20 

21.8 

23.6 

25.4 

2 

8.9 

11.1 

13.3 

15.5 

17.7 

20 

22.2 

24.4 

26.6 

28.8 

31 

10.6 

132 

15.9 

185 

21.2 

23.8 

26.6 

29.1 

31.8 

34.4 

37 

2J4 

12.6 

15.8 

19 

22 

25 

28 

31 

35 

38 

41 

44 

2% 

15 

18 

22 

26 

29 

33 

37 

41 

44 

48 

62 

2V£ 

17 

21 

26 

30 

34 

39 

43 

47 

52 

56 

60 

2% 

23 

29 

34 

40 

46 

52 

58 

64 

69 

75 

81 

3 

30 

37 

45 

52 

60 

67 

75 

82 

90 

97 

105 

38 

47 

57 

66 

76 

85 

V5 

104 

114 

123 

(33 

3J4 

47 

59 

71 

83 

95 

107 

119 

131 

143 

155 

167 

334 

58 

73 

88 

102 

117 

132 

146 

162 

176 

190 

2^5 

4' 

71 

89 

107 

125 

142 

160 

178 

196 

213 

231 

249 

TRANSMITTING  EFFICIENCY  OF  TURNED  IRON  SHAFTING  AT  DIFFERENT  SPEEDS. 

For  Simply  Transmitting  Power. 


Diameter  of  Shaft. 

Number  of  Revolutions  per  Minute. 

100 

125 

150 

175 

200 

233 

267 

300 

333 

367 

400 

Inches. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

1/4 

6.7 

8.4 

10.1 

11.8 

13.5 

15.7 

17.9 

20.3 

22.5 

24.8 

27 

1% 

8.6 

10.7 

12.8 

15 

17.1 

20 

22.8 

25.8 

28.6 

31.5 

34.3 

1% 

10.7 

13.4 

16 

18.7 

21.5 

25 

28 

32 

36 

39 

43 

Ij2 

13.2 

16.5 

19.7 

23 

26.4 

31 

35 

39 

44 

48 

52 

2 

16 

20 

24 

28 

32 

37 

42 

48 

53 

58 

64 

2^ 

19 

24 

29 

33 

38 

44 

51 

57 

63 

70 

76 

2/4 

22 

28 

34 

39 

45 

52 

60 

68 

75 

83 

90 

2$B 

27 

33 

40 

47 

53 

62 

70 

79 

88 

96 

105 

2J4 

31 

39 

47 

54 

62 

73 

83 

93 

104 

114 

125 

2% 

41 

52 

62 

73 

83 

97 

111 

125 

139 

153 

167 

3 

54 

67 

81 

94 

108 

126 

144 

162 

180 

198 

216 

3^ 

68 

86 

103 

120 

137 

160 

182 

205 

228 

250 

273 

*& 

85 

107 

128 

150 

171 

200 

228 

257 

285 

313 

342 

TABLES    AND    USEFUL   DATA. 


•_ 
<w  * 
Cj 

|S 

i 

! 

r.1,  .'..'.,,:,„•,.  .,i 

s 

s»isiMt'ain»n 

p   - 
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5  ~  - 

a  1 

• 

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i§i!!S 

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S  i  5  |  2  S  1  *  §  i  1 

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llilllllllil 

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542 


MODERN    MACHINE    SHOP    TOOLS. 


CAPACITY  OP  BOUND  TANKS  AND  CYLINDERS  IN  CUBIC  FEET  AND  IN  U.  S.  GALLONS. 

(FROM  TRAUTWEIN.) 

Of  231  cubic  inches  (or  7.4805  gallons  to  a  cubic  foot)  ;  and  for  one  foot  of  length  of 
the  cylinder.  For  the  contents  for  a  greater  diameter  than  any  in  the  table  take  the 
quantity  opposite  one-half  said  diameter,  and  multiply  it  by  4.  Thus,  the  number  of 
cubic  feet  in  one  foot  length  of  a  pipe  80  inches  in  diameter  is  equal  to  8.728x4=34.912 
cubic  feet.  So  also  with  gallons  and  areas. 


OQ 

For  1  foot 

03 

For  1  foot 

S 

For  1  foot 

1 

o 

I 

in  length. 

1 

i 

a 

in  lenjrth. 

g 

| 

• 

in  length. 

a 

1*3 

a 

S  ' 

S^j 

,_| 

a 

•§8 

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85 

'a 

T3  O 

£$ 

§3  . 

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£^"11 

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11 

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03 

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0-9 

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5 

S 

005 

O 

B 

5 

uS 

O 

S 

S 

Ss 

S 

¥ 

.0208 

.0003 

..0026 

6% 

.5625 

.2485 

1.859 

19 

1.583 

1.969 

14.73 

.0260 

.0005 

.0040 

7 

.5833 

.2673 

1.999 

19^6 

1.625 

2.074 

15.52 

SZ 

.0313 

.0008 

.0057 

7J4 

.6042 

.2868 

2.144 

20 

1.666 

2.182 

16.32 

T7S 

.0365 

.0010 

.0078 

?H 

.6250 

.3068 

2.295 

1.708 

2.292 

17.15 

1£ 

.0417 

.0014 

.0102 

7% 

.6458 

.3275 

2.450 

21  8 

1.750 

2.405 

17.99 

T9B 

.0469 

.0017 

.0129 

8 

.6667 

.3490 

2.611 

1.792 

2.521 

18.86 

% 

.0521 

.0021 

.0159 

8/4 

.6875 

.3713 

2.777 

22  S 

1.833 

2.640 

19.75 

11 

.0573 

.0026 

.0193 

8J4 

.70^3 

.3940 

2.948 

22^ 

1.875 

2.761 

20.65 

94 

.0625 

.0031 

.0230 

8% 

.7292 

.4175 

3.125 

23 

1.917 

2.885 

21.58 

13 

.0677 

.0036 

.0270 

9 

.7500 

.4418 

3.305 

2-{L£ 

1.958 

3.012 

22.53 

% 

.0729 

.0042 

.0312 

9M 

.7708 

.4668 

3.492 

24  " 

2.000 

3.142 

23.50 

IB 

.0781 

.0048 

.0359 

<»L£ 

.7917 

.4923 

3.682 

25 

2.083 

3.409 

25.50 

1 

.0833 

.0055 

.0408 

9% 

.8125 

.5185 

3.879 

26 

2.166 

3.687 

27.58 

m 

.1042 

.OC85 

.0638 

10 

.8333 

.5455 

4.081 

27 

2.250 

3.976 

29.74 

ig 

.1250 

.0123 

.0918 

10V4 

.8512 

.5730 

4.286 

28 

2.333 

4.276 

31.99 

.1458 

.0168 

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10^4 

.8750 

.6013 

4.498 

29 

2.416 

4.587 

34.31 

24 

.1667 

.0218 

.1632 

lOfc 

.8958 

.6303 

4.714 

30 

2.500 

4.909 

36.72 

.1875 

.0276 

.2066 

ilr 

.9167 

.6600 

4.937 

31 

2.583 

5.241 

39.21 

"2J4 

.2083 

.0341 

.2550 

.9375 

.6903 

5.163 

32 

2.666 

5.585 

41.78 

2§4 

.2292 

.0413 

.3085 

11/4 

.9583 

.7213 

5.395 

33 

2.750 

5.940 

44.43 

3 

.2500 

.0491 

.3673 

11*4 

.9792 

.7530 

5.633 

34 

6.305 

47.17 

3/4 

.2708 

.0576 

.4310 

32 

1  foot 

.7854 

5.876 

!<5 

2'.916 

6.681 

49.98 

3^ 

.2917 

.06fi8 

.4998 

1.042 

.8523 

6.375 

36 

3.000 

7.089 

52.88 

3% 

.3125 

.0767 

.5738 

13 

.083 

.9218 

6.895 

37 

3.083 

7.468 

55.86 

4 

.3333 

.0873 

.6528 

13/4 

.125 

.9940 

7.435 

38 

3.166 

7.876 

58.92 

.3542 

.0985 

.7370 

14 

.167 

1.069 

7.997 

39 

3.250 

8.296 

62.06 

4)4 

.3750 

.1105 

.8263 

14Vja 

.208 

1.147 

8.578 

40 

3.333 

8.728 

65.29 

4:!4 

.3958 

.1231 

.9205 

15 

.250 

1.227 

9.180 

41 

3.416 

9.168 

68.58 

.5 

.4167 

.1364 

1.020 

15/^ 

.292 

1.310 

9.801 

42 

3.500 

9.620 

71.95 

514 

.4375 

.1503 

1.124 

16 

.333 

1.396 

10.44 

43 

3.583 

10.084 

75.43 

5  Hi 

.4583 

.1650 

1.234 

16J^ 

.375 

1.485 

11.11 

44 

3.666 

10.560 

79.00 

•5% 

.4792 

.1803 

1.349 

17  ~ 

.417 

1.576 

11.79    ' 

45 

3.750 

11.044 

82.62 

6 

.5000 

.1963 

1.469 

.458 

1.670 

12.50 

46 

3.833 

11.540 

8ri.32 

*>V4 

.5208 

.2130 

1.594 

18  3 

.500 

1.767 

13.22 

47 

3.916 

12.048 

90.12 

6J| 

.5417 

.2305 

1.724 

.542 

1.867 

13.97 

48 

4.000 

12.566 

94.02 

CAPACITIES  OF  RECTANGULAR  TANKS  IN  UNITED  STATES  GALLONS,  FOR  EACH 
FOOT  IN  DEPTH. 


^           M 

~           — 

S'Sg 

fc  6 

Length  of  Tank. 

Feet. 
2 
29.92 

Ft.  In. 
2    6 

37.40 
46.75 

Feet. 
3 

44.88 
56.10 
67.32 

Ft.  In. 
3    6 

52.36 
65.45 
78.54 
91.64 

Feet. 
4 

59  84 
74  80 
89.77 
104.73 
119.69 

Ft.  In. 

4    6 

~67.32 
84.16 
100.99 
117.82 
134.65 
151.48 

Feet. 
5 

~74.81 
93.51 
112.21 
130.91 
149.61 
168.31 
187.01 

Ft.  In. 
5    6 

82J*T 
102.86 
123.43 
144.00 
164.57 
185.14 
205.71 
226.28 

Feet. 
6 

~89.77~ 
112.21 
134.65 
157.09 
179.53 
201.97 
224.41 
246.86 
269.30 

Ft.  In. 
6    6 

97.25 
121.56 
145.87 
170.18 
194.49 
218.80 
243.11 
267.43 
291.74 
316.05 

Feet. 

7 

104.73 
130.91 
157.09 
183.27 
209.45 
235.«3 
261.82 
288.00 
314.18 
340.36 

Ft.In. 

~2    — 
2     6 
3    - 
3     6 
4    — 
4     6 
5    — 
5     6 
6    - 
«     6 

TABLES   AND    USEFUL   DATA, 


543 


METRIC    CONVERSION    TAJ 

Arranged  by  C.  W.  Hunt,  New  York. 


Millimeters  X  .03937  =  inches. 

Millimeters  -*-  25.4  =  inches. 

Centimeters  X  .3937  =  inches. 

Centimeters  •+-  2.54  =  inches. 

Meters  X  39.37  =  inches.  (Act  Congress.) 

Meters  X  3.281  =  feet. 

Meters  X  1.094  =  yards. 

Kilometers  X  .621  =  miles. 

Kilometers  -*-  1.61.93  =  miles. 

Kilometers  X  3280.7  =  feet. 

Square  Millimeters  X  .0155  =  sq.  inches. 

Square  Millimeters  •*-  645.1  =  sq.  inches. 

Square  Centimeters  X  .155  =  sq.  inches. 

Square  Centimeters  -*-  6.451  =  sq.  inches. 

Square  Meters  X  10.764  =  sq.  feet. 

Square  Kilometers  X  247.1  =  acres. 

Hectare  X  2.471  =  acres. 

Cubic  Centimeters  -s- 16.383  =  cubic  inches. 

Cubic  Centimeters  H-  3.69  =  fl.  drachms. 

(U.S.  P.) 

Cubic  Centimeters  -*-  29.57  =  fl.  oz.  (U.S.P.) 
Cubic  Meters  X  35.315  =  cubic  feet. 
Cubic  Meters  X  1.308  =  cubic  yards. 
Cubic  Meters  X  264.2=  gallons  (231  cu.  in.) 
Liters  X  61.022=  cubic  in.  (Act  Congress.) 
Liters  X  33  84  =  fluid  ounces  (U.  S.  Phar.) 
Liters  X  .2642  =  gallons  (231  cu.  in.) 
Liters  -*-  3.78  =  gallons  (231  cu.  in.) 
Liters  -*-  28.316  =  cubic  feet. 
Hectoliters  x  3.531  =  cubic  feet. 


Hectoliters  x  2.84  =  bushels  (2150.42  cu.in. 

Hectolite«s  X  .131  =  cubic  yards. 

Hectoliters  -*-  26  42  =  gallons  (231  cu.  in.) 

Grammes  x  15.432  =  grains.(Act  Congress.) 

Grammes  -+•  981  =  dynes. 

Grammes  (water)  -*-  29.57  =  fluid  ounces. 

Grammes  -*-  28.35  =  ounces  avoirdupois. 

Grammes  per  cu.  cent.  -*-  27.7  =  Ibs.  per 
cu.  in. 

Joule  X  .  7373  =  foot  pounds. 

Kilogrammes  X  2.2046  =  pounds. 

Kilogrammes  X  35.3  =  ounces  avoirdu- 
pois. 

Kilogrammes  -5- 1102.3  -  tons  (2,000  Ibs.) 

Kilogrammes  per  fcq.  cent,  x  14.2.3  =  Ibs. 


per  sq.  in. 
QDn 


Kilogram-meters  X  7.233  =  foot  Ibs. 

Kilo  per  Meter  X  .672  =  Ibs.  per  foot. 

Kilo  per  Cu.  Meter  x  .062  =  Ibs.  per  en.  ft. 

Kilo  per  Cheval  X  2.235  =  Ibs.  per  H.  P. 

Kilo- Watts  X  1.34  =  Horse  Power. 

Watts  -s-  746.  =  Horse  Power. 

Watts  -H  .7373  =  foot  pounds  per  second. 

Calorie  X  3  968  =  B.  T.  U. 

Cheval  vapeur  X  .9863  =  Horse  Power. 

(Centigrade  x  L8)  +  32  =  degree  Fahren- 
heit. 

Franc  X  .193  =  Dollars. 

Gravity  Paris  =  980.94  centimeters  per 
second. 


DATA  ON  WATER. 

cubic  foot  of  water  = 1 62.3791  Ibs. 

cubic  inch  of  water  = 03612  Ibs. 

gallon  of  wa>er  =  8.338     Ibs. 

gallon  of  water  = 231.          cubic  in. 

cubic  foot  of  water  = 7.480     gallons. 

pound  of  water  = 27.7        cubic  in. 

The  above  data  is  calculated  for  distilled  water  at  40°  Fahrenheit. 
The  pressure  of  a  column  of  water  in  pounds  per  square  inch  is  equal  to  the  height 
of  the  column  in  feet  multiplied  by  .433. 

The  pressure  per  square  foot  is  equal  to  the  height  of  th°  column  in  feet  multi- 
plied by  62.44  The  power  required  to  elevate  water  is  equal  to  the  weight  of  the 
water  multiplied  by  the  height  in  feet  through  which  it  is  lifted  (foot  pounds)  divided 
by  33,OOJ.  An  allowance  of  25  per  cent  should  ordinarily  be  made  for  frictional  losses. 


DATA  ON  POWER. 

The  Unit  of  Work  is  the  foot  pound  or  the  work  necessary  to  raise  a  weight  of 
one  pound  one  foot. 

The  Unit  of  Heat  is  the  British  Thermal  Unit  or  the  amount  of  heat  necessary  to 
raise  the  temperature  of  one  pound  of  pure  water  from  39°  to  40°  Fahrenheit. 

The  Mechanical  Equivalent  of  one  British  Thermal  Unit  of  he  it  is  778  foot  pounds 
of  work,  and  upon  this  value  are  based  all  heat  and  power  determinations. 

A  Horse  Power  is  the  amount  of  work  necessary  to  raise  33,000  pounds  one  foot 
high  in  one  minute.  It  is  dependent  upon  three  factors :  force,  distance  and  time. 

Indicated  Horse  Power  is  the  measure  of  tie  work  developed  in  the  cylinder  of 
an  engine  and  equal  to  the  following  expression  : 


Horse  Power 


Pressure  X  Area  X  Double  Stroke  X  Revolutions 
33,000 


where  pressure  =  the  mean  or  average  pressure  per  square  inch  on  the  piston :  Area 
=  the  area  of  the  piston  in  square  inches ;  Double  Stroke  —  the  distance  traveled  by 
the  piston  in  feet  for  each  revolution,  and  Revolutions  =  the  number  of  re  volutions 
the  engine  makes  in  one  minute.  In  this  expression  the  pressure  and  area  represent 
the  force,  and  the  stroke  and  revolutions  the  distance. 

Brake  Horse  Power  is  the  measure  of  the  power  given  off  at  the  shaft,  and  is 
always  le?s  than  the  indicated  horse  power  by  an  amount  equal  to  the  work  necessary 
to  overcome  the  frictional  resistance  of  the  engine.  In  measuring  the  brake  horse 
power  a  suitable  brake  is  applied  to  the  fly  wheel  of  the  engine  as  shown  in  Fig.  673. 


544 


MODERN    MACHINE   SHOP    TOOLS. 


A  band  a  a  a  a  of  rope,  leather  or  steel  is  placed  on  the  wheel.  The  rod  R  attached  to 
the  brake  at  the  distance  L  from  the  center  of  rotation  holds  the  brake  from 
rotating  with  the  wheel.  This  rod  is  attached  to  a  suitable  scale  beam  by  means  of 
which  the  pull  P  can  be  weighed.  By  means  of  the  nut  H  and  screw  S  the  brake  can 
be  adjusted  to  absorb  the  full  power  of  the  engine. 

We  then  have  a  force  P  acting  through  a  distance  represented  by  the  radius  L  and 


(L 


FIG.    673. 


the  number  of  revolutions  the  wheel  makes,  or,  in  other  words,  the  distance  the  point 
P  would  move  in  one  minute  if  free  to  turn. 

force  X  distance       P  x  2L  X  T  X  N 
The  brake  horse  power  =  horsepower  =  _____  =     ___ 

when  P  =  the  force  in  pounds ;  2L  =  the  diameter  in  feet  of  the  circle  through  which 
the  force  acts $  •*  =  the  constant  3. 1416  by  which  the  diameter  is  multiplied  to  obtain 
the  circumference,  and  N  =  the  number  of  revolutions  per  minute. 


INDEX. 


Addendum   circle    465 

Adjustable  hollow  milling  tool 208 

Adjustable   reamers    114,  120 

Adjustable    limit    gauges 91 

Adjustable  dies 136 

Advantage   of   radial    mills 318 

Advantage  of  collapsing  taps 133 

Advantages  of  expansve  mandrels.  .    158 
Advantages  of  patent  lathe   tools.  .    201 

Alining    shafting 512 

Angular  and  notch  gauges 84 

Angular  milling  cutters 336,  339 

Angular   velocity    463 

Angular    drilling    415 

Arbors    : 154 

Arbors,     milling     348 

Arbors,   shell   end   mill 346 

Arbors,   thread    347 

Arch  stays 462 

Automatic  gear   cutting  machines.  .   384 
Automatic  screw  machine    .  .    191 


Back   facing    415 

Back  gearing,  computation  of 167 

Back  gear,  friction 191 

Back    gearing,    triple 167 

Back   lash,   effect  of  on   taper  turn- 
ing       230 

Balancing  of  pulleys    521 

Balancing    way     521 

Bearing,    shaft    511 

Bell    center    punch 220 

Ball   turning    243 

Belting    490 

Belting,  care  of  leather 493 

Belting,    double,    triple,    etc 492 

Belting,  examples  of  drives 497 

Belting,   hides  used  for   leather....    490 

Belting,   leather    490 

Belting,  leather  strongest  section  of  492 

Belting,   methods  of  lacing 495 

Belting,  methods  of  lapping.  ......   494 

Belting,  power  transmitted  by 493 

Belting,  preparation  of  leather 491 

Belting,    reasons    for    running    hair 

side  next  to  the  pulley 496 

Belts,  run  of  on  pulleys 501 

Bevel  gear  cutting    365-387 

Bevel    gear    cutting   in    milling    ma- 
chine         365 

Bevel  gear  cutting,  selecting  of  cut- 
ters for    382 

Bevel  gears   467 

Bevel  gears,   laying  out 474 

Bevel  gear  planer,  Belgram 392 

Bevel  gear  planer,.  Gleason 392 

Blocking   for   planer 299 

Bolts,  carriage   450 

Bolts,    machine    450 

Bolts,    stud    451 

Boring  bars    250 

Boring  large  parallel  holes  in  heavy 

drilling  machines 420 

Boring  mills,  floor   268 


I  Boring  mills,  horizontal    26S 

I  Boring  mills,  relation  to  the  lathe.    i^u-l 

i  Boring  mills,  universal    26i> 

Boring  mill  work,  securing 26i> 

:  Boring  parallel  holes  in  the   lathe     25s> 

i  Boring  mills,  vertical 

Boring,    setting   up    work    for 

Boring   spherical    sockets 

Boring    tapered    holes    with    boring 

bars     252 

Boring    tools    200-202-203 

Boring    work    secured    to    the    lathe 

carriage     252 

Box  cut-off  slide    20i> 

Box  tools 207 

Buffing    spindle     425 

Bushings,    for   jigs    41O- 

Brazing  furnace   522 

Brown   and   Sharpe  tapers 346. 


Circulating  speed  of  pulleys 514 

Calculation  of  cutting  speeds 224: 

Calculations   for    indexing   on    auto- 
matic gear   cutters    386 

Caliper  dividers   22O 

Calipers     64 

Calipers,   firm   joint 64 

Taliper    gauges     60" 

Calipers,    hermaphrodite 68. 

Calipers,  how  held 65 

Calipers,  keyhole    68. 

Calipers,  lock  joint   64 

Calipers,    micrometer    70> 

Calipers,  recording   64 

Calipers,   spring  joint    65 

Calipers,  thread 68 

Calipers,  transfer,  types  of 64-68 

Calipers,    use   of    65-67 

Calipers,    vernier    68 

Cam  cutting  attachment 333 

Cam     milling,     example    of 37ft 

Cape    chisels     2<> 

Case    hardening    448 

Care  in  heating  tool  steel 446 

Care  in   indexing    353 

Care  and  use  of  drill   chucks 151 

Care  of  centers 23ft 

Care    of    files    45 

Care  of  lathe  centers 181 

Care  of  mandrel   centers    161 

Care  of  surface  plates ">4 

Care  necessary  in  chucking 255 

Care  to  exercise  in  putting  on  arbor 

cutters    361 

Carriage   bolts    45<> 

Cat  head    22ft 

Causes  of  inaccurate  work  with  flat 

drills     104 

enter  bearing  reamers 123 

'enter  bearings,  form  of 222 

Center   bearings,    lubrication   of.  ...    222 

Center  gauges 86 

Center  head  square,  use  of 221 

Center     reamer,     combination 222 

Oenter    rest     225 

Center  rest  work,  example  of 227 


546 


INDEX. 


Centers,  care  of 23b 

Centers,   drawing   over    222 

Centers,    drilling   of 222 

Centers,   pipe    238 

Centers,     index 29b 

Centers,  locating  of 220 

Centers,  planer 29b 

Check    nuts 4ol 

Chucking  reamers   lib,  1 

Circular  milling  attachment   330 

Circular    pitch    46o 

Clamp  dogs •  •  £11 

Clamping  work  on  planer    299-301 

Clamps,   helt    494 

Clamps  for  planer    300 

Classes  of  milling  cutters 3ob 

Classification   of  drilling  jigs 410 

Classification  of  files 25 

Classification  of  grinding  operations  423 

Cleaning  castings 46 

Cleaning  files    

Clearance  angle    198 

Clearance  in  tap  threads Ibl 

Clearances  in  twist  drills 105 

Cold  chisels,   forms  of    

Cold  chisels,  how  forged 18 

Cold  chisels,  correct  grinding  of...  19 

Cold  chisels,  how  held    21 

Cold   chisels,   machinist    18 

Cold  chisels,   temper  of 21 

Cold    chisel,    tempering   of 446 

Collet   chucks    195 

Collets,    milling   machine    346 

Collets,   spring  chuck    „ 348 

Combination  'center   reamer    222 

Combination  drill  and  pipe  taps.  .  .  .  133 

Combination    chucks    216 

Combination  squares   

Comparison  of  wire  gauges 82 

Combination  wrenches 3  02 

Compound   indexing    351 

Compound    rest    170 

Compressed  air  in  the  shop 517 

Computation  of  back  gearing    167 

Cones,   rapid  finishing  of 259 

Correct  grinding  of  cold  chisels.  ...  19 

Correct  use  of  hack  saw  blades.  ...  99 

Correct  use  of  hammers 18 

Correct  use  of  monkey  wrenches.  .  .  100 

Cotter    pins     458 

Counter  bore 415 

Counter  shafts   196 

Couplings,    shaft    508 

Change  gears  in  gangs   177 

Chucking,  care  necessary  in 255 

Chucking    work     254 

Chucking  work  from  outside 255 

Chucks,    drill     150 

Chucks,  drill,  care  and  use  of 151 

Chucks,    combination     216 

Chucks,   face  plate    218 

Chucks,    independent     215 

Chucks,    lathe     214 

Chucks,    revolving    219 

Chucks  for  special  work 254 

Chucks  split    266 

Chucks,    universal     215 

Collapsing   taps,   advantages   of.  ...  133 

Crank  driven  shapers   283 

Crank   pins,    turning   of 232 

Cross-filing    30 

Cross  sections  of  files 22 

Cutter  and  reamer  grinder 425 

Cutter  bar  for  keyseater    310 

Cutter  head  for  boring 270 

Cutters,  care  to  exercise  in  putting 

on   arbor    361 

Cutters  for  keyseaters    309 

Cutters,      importance      of      keeping 

sharp    356 

Cutters,  milling,  driving  of 349-359 

Cutting  angle  for  drills 106 


Cutting  bevel  gear 365-387 

Cutting   edges    197-199 

Cutting  double   threads    235 

Cutting  key   ways    364 

Cutting  worm  gears 365 

Cutting  off  machine    196 

Cutting  speeds    223 

Cutting  off  tools    200 

Cutting  speeds,   calculation   of 224 

Cutting  speeds,   effect   upon   output.  224 

Cutting  spiral  gears 394 

Cycloidal   curve    472 

Cycloidal   gearing   system 467,  471 

Cycloidal   tooth  curves    472 

Cylinder  boring,  example  of   271 

Cylinder    boring    machine     270 

Cylindrical   grinding    428 


Uata   for    spiral   gears 482 

Data  on  water   542 

Definition   of  forced  fit    262 

Definition  of  horse  power 542 

Definition   of  working  fit 262 

Diametral    pitch     465 

Diamond  point  chisels 21 

Diamond  truers    437 

Die  sinking  machine   320 

Dies,    adjustable    136 

Dies,    two    classes   of    135 

Dies^  effect  of  tempering  on 140 

Dies,    self-opening    138 

Dies,    how    sharpened    137 

Dies,   solid    136-138 

Dies,  use  of  on  oversize  stock 140 

Dimensions  of  lathe    1<7 

Dividing    mechanism    on    automatic 

gear   cutters    386 

Dogs,   clamp    211 

Dogs,  die   211 

Dogs,  double  end    211 

Dogs,   lathe    210 

Dogs,  effect  of  leverage  on  the  work  210 

Double    cut   files    25 

Double   threads,   cutting   of 235 

Draw  filing    39 

Draw   filing,   accuracy   of    40 

Drawing  of  keys    457 

Drawing    over    centers    222 

Dressing       and       regrinding       ham- 
mers      18 

Drift   drill    134 

Drill    and   tap   holders,   reversing.  .  .  148 
Drill    and    tap    holders,    importance 

of    142 

Drill  chucks 150 

Drill    chuck,    "Presto." 149 

Drill    feeds    HO 

Drill    lubrication    HO 

Drill,   pod    414 

Drill  shanks   108 

Drill    sockets     142 

Drill  speeds,  rule  for   HO 

Drill  sizes   109 

Drills,    flat    103 

Drilled  holes,   locating    112 

Drilling  attachment,  high  speed   .  .  .  407 

Drilling  large  holes  in  plates 415 

Drilling    jigs     410 

Drilling,    annular     415 

Drilling  of  centers 222 

Drilling   machines    397 

Drilling    machine,    pneumatic 518 

Drilling     machines,     standard     pat- 
tern       397 

Drilling,    starting   drill    true   in    the 

lathe    249 

Drilling  of  deep  holes 414 

Drilling    jigs     410 

Drilling  in  the  lathe    248 


INDEX. 


547 


Drilling  machine,  manufactures 406 

Drills  ioi-  brass  work  110 

Drills  with  "constant"  angle  of 

flute  >w  107 

Drills,  forged  106 

Drills  with  hollow  shanks  108 

Drills  with  grooved  shanks  109 

Drills,  causes  of  inaccurate  work 

with  flat  104 

Drills,  gang 400 

Drills,  horizontal  spindle  40o 

Drills,  multiple  spindle  399 

Drills,  oil  tube  Ill 

Drills,  oil  tube,  use  of 248 

Drills,  portable  405 

Drills,  radial  401 

Drills,  rolled  106 

Drills,  straight  flute  107 

Drills,  three-flute  107 

Drills,  twist  105 

Drilling  tables,  universal  403 

Drilling  vise  .  .  , 408 

Drivers,  notch  -13 

Drivers,  nut  212 

Drivers  for  threaded  work 212 

Drivers,  pulley  213 

Driving  fit,  allowance  for 202 

Driving  fit,  definition  of  262 

Driving  large  work  on  the  mandrel.  160 

Dummy,  use  of  in  turning  cams.  .  .  246 

Duplex  gear  cutters  383 

Duplex  milling  machine  317 


i: 


Electric   transmission   of  power.  ...  515 

Emery  wheels 429 

Emery  wheel  dressers 437 

Emery   wheels,   selecting  of  for  any 

class  of  work    430 

Emery  wheels,  speed  of   430 

Epicycloidal    curve     472 

Effect  of  carbon  in  steel 440 

Effect  of  sand  and  scale   on  files..  46 

Effect  of   tempering  on  dies    140 

Efficiency   of   toothed   gearing 474 

Elements  of  lathe 165 

Elements  of  spiral  gears 479 

End    measure    gauges 59 

Engine    lathe     165 

Example  of  center  rest  work 227 

Example  of  heavy  gang  milling.  .  .  .  372 

Example   of  heavy   turret   work.  .  .  .  258 

Example   of  slotting   machine   work.  307 

Example   of  cam   milling 376 

Examples   of  jig   milling 374 

Examples   of  vertical   milling 370 

Example   of   box   jig 412 

Examples  of  jigs    411 

Example  of   turret   facing 257 

Exercise  of  judgment  in  turning.  .  .  .  224 

Expanding  mandrels 154-156 


Face  plate  carriers 255 

Face  plate  chucks 218 

Facing   in    boring   mill 272 

Facing  work  in  the  milling  machine  363 

Fastenings    450 

Fastenings  for  screw  threads 125 

Feather  keys 455 

Feather,   sliding    455 

Feeds,  automatic  vertical   for  shap- 

ers     285 

Feed  gear  reversal 173 

Feed   rods    171 

Feeds   for   milling    356 

Feeds,    geared     1 72 

Fellows  gear  shaper    389 


File  handles    32 

File  holders,  surface :;_ 

File  teeth,  effect  of  form   of 27--.S 

Files,  annealing  of  blanks   25 

Files,   blank   forms 23-24 

Files,  care  of 45 

Files,    cleaning   of 44 

Files,  cross  sections  of 22 

Files,   classification  of    25 

Files,  double  cut 25 

Files,  effect  of  sand  and  scale  on.  .  46 

Files,   grades  as  to   coarseness 25 

Files,  hand  cut 27 

Files,  how  held  in  operating 31-38 

Files,   lengths 23 

Files,  machine  cut 26 

Files,    names   of 22-23 

Files,  necessity  of  belly  in 29 

Files,  pinning  of    45 

Files,  preparation  of  blanks  for  cut- 
ting    25 

Files,   racks  for 46 

Files,   rasp    25 

Files,  safety  edges  on 36 

Files,   selecting  of,  for  any  class  of 

work    30-34-46 

Files,  single  cut 25 

Files,  use  of  chalk  and  oil  on 45 

Filing,  direction  of  strokes 34 

Filing,   effect  of  narrow   surface  on 

file  teeth    34 

Filing,  fillets 37 

Filing,   flat   surfaces    .  : 35 

Filing,    interior    surfaces    36 

Filing,   mortises    38 

Filing,  position  of  work  for 33 

Filing  rotating  discs   44 

Filing   rotating   work    41 

Filing,  position  of  workman 33 

Filing  square  corners    37 

Filing  square  and  round  holes 35 

Filing  thin  work 39 

Finishing  cuts  after  roughing 253 

Filtering   of   oil    523 

Finishing   for   planer    tools    293 

Fitting    surfaces    by    "bedding"....  52 

Flat  drills 103 

Flat    keys    455 

Flat  turret  lathe    194 

Fly    cutter    342 

Follow  rest .  227 

Forced  fit.  definition  of 262 

Forged    drills    106 

Formed    cutters    243 

Formed    gear    cutters 381 

Forming    tools    207 

Form  of  center  bearings 222 

Forms  of  cold  chisels    20 

Form  of  flutes  and  teeth  taps 131 

Forms  of  hammers    17 

Forms    of   scrapers    48 

Frictional    tap    holders 147,  149 

Frlctional  gearing   463 


Gang  drill  work,  examples  of 416 

Gang  drills    400 

Gang  drilling  jigs    417 

Gang  milling  cutters 313 

Gang  milling,  example  of  heavy.  . .  .   372 

Gang   milling,    importance   of 313 

Gang  planer  tools 291 

Gauges,  adjustable  limit 90 

Gauges,  angular  and  notch   84 

Gauges,  caliper 60 

Gauges,    center     86 

Gauges,   corrective    62 

Gauges,  depth 89 

Gauges,    drill     84 

Gauges,  end  measure   59 


INDEX. 


Gauges,  limit    61 

Gauges,  manufacture  of 63 

Gauges,  nut  and  washer 85 

Gauges,   plug  and   ring 59 

Gauges,   scratch    89 

Gauges,  screw  thread 88 

Gauges,  standard  care  in  use  of .  .  .      61 

Gauges,  standard   59 

Gauges,  standard  thread t>2 

Gauges,   surface    90 

Gauges,    thickness    88 

Gauges,  thread   8V 

Gauges,  use  of 61 

Gauges,    wire    85 

Gear    cutters    340 

Gear  cutting,  duplication  system...    379 

Gear   cutters,    duplex    383 

Gear  cutters  in  gangs    383 

Gear    cutting    in    plain    milling    ma- 
chine, by   under  cut  method .  .  .   365 
Gear    cutting,    laige    spur,    in   plain 

milling  machine    365 

Gear  cutting  machines,  automatic..    384 
Gear       cutting,       molding      planing 

method    380 

Gear       cutting,       templet       planing 

method    380 

Gear    shaper,    Fellows    389 

Gears,  bevel 467 

Gears,   toothed    464 

Gears,   worm    467-475 

Gearing    463 

Gearing,   cycloidal,   system 467-471 

Gearing,  efficiency  of  toothed 474 

Gearing,   f  rictional    463 

Gearing,   involute   system 467 

Gears,  internal   473 

Gears    with    axes    at    varying    dis- 
tances         471 

Gears,    spiral    467 

Gears,  spur 467 

Graduated  dials  on  feed  screws,  use 

of    362 

Graduate  machine  dials,  value  of.  .    378 

Grinder,  cutter  and  reamer 425 

Grinder,  twist  drill    428 

Grinding,  cylindrical    428 

Grinding,   importance   of    423 

Grinding,    internal    429-433 

Grinding  machine,  plain    293-429 

Grinding  machine,   universal    428 

Grinding  operations,  classification  of  423 

Grinding  steep  tapers   434 

Grinder,   portable    437 

Grinder,    tool    424 


Hack  saw  blades 99 

Hack  saw  blades,  correct  use  of .  .  .  99 

Hack  saw  frames 100 

Hack  sawing  machines   520 

Hammers,  correct  use  of 18 

Hammers,  dressing  and  regrinding.  .  18 

Hammers,    forms    of 17 

Hammer  handles    18 

Hammers,  machinist 17 

Hammers,    pneumatic    518 

Hammers,   weight   of 17 

Hand   cut   files 27 

Hand    caps    129 

Handles,  of  hammers 18 

Hardening  in  oil 443 

Hardening  in   steel 440 

Heat,  unit  of 542 

Heating   of   steel 443 

Heating  of  tool  steel,  care  in 446 

Hermaphrodite    calipers 220 

Hides  used  for  leather  belting 490 

High  speed  milling  attachment. 331,  407  i 

Hints  on  planer  manipulation 305  I 


Hobbing    machine    393 

Hobs,    worm     340,    365-393 

Hoists,    hand 520 

Hoists,   pneumatic    517 

Hollow   hexagon    turret    lathe 196 

Hollow  milling  tool,  adjustable 208 

Horse    power,    brake 542 

Horse   power,    definition    of 542 

Horse  power,  indicated 542 

ilorse  power,  measuring  of 542 

How  to  find  tap  drill   sizes 141 

How  to  sharpen  dies    137 

Hypocycloidal   curve    472 


Importance  of  drill  and  tap  holders.  142 

Importance  of  gans  milling 313 

Importance  of  grinding 423 

Importance  of  keeping  sharp  cutters  356 
Importance  of  milling  machines....  312 

Increase  twist  in  drills 106 

Independent  chucks 215 

Indexing,  care  in 353 

Indexing,  centers 323 

Indexing,  compound 351 

Indexing,  differential 352 

Indexing  on  automatic  gear  cutters, 

calculations  for  386 

Indexing,  plain  324 

Indexing,  rule  for 350 

Indicator,  use  of  test 92 

Influence  of  form  and  number  of 

teeth  in  reamers  114 

Inside  micrometer  calipers 81 

Internal  grinding 433 

Involute  curve  467 

Involute  tooth  outline,  approximate 

method  of  laying  out 468 


Jacks,   planer    300 

Jig,    box,    example    of 412 

Jigs,  drilling,  classification  of 410 

Jigs    examples  of 411 

Jigs,  for  drilling 410 

Jigs  of  gang  drilling 417 

Jig   milling,   example  of 374 


Key  rule  blocks 97 

Key    seater 308 

Key   seaters,  portable 311 

Key  seating  in  a  shaper 298 

Key  ways,   cutting  of 364 

Keys,  drawing  of 457 

Keys,    flat    455 

Keys,  gib  head 457 

Keys,    round    454 

Keys,   taner  of 455 

Keys,     Woodruff 456 

Knee  plate,  securing  work  to 254 

Knee  plate,  use  of 375 

Knurling    tools 206 


Large    micrometer    calipers 74 

Lapping     438 

Laps     431) 

165 
169 
181 
174 
175 
175 


Lathe  beds    

Lathe  carriage    

Lathe  centers,  care  of 

Lathe  change  gears 

Lathe   change  'gear   calculations 
Lathe   change   gears,   compound 


INDEX. 


549 


Lathe    chucks -14 

Lathe,   dimensions  of    .  .  .  . ITT 

Lathe  dogs  .- 'JlO 

Lathe,  elements  of 165 

Lathe,  engine  165 

Lathe,    gap    184 

Lathe   head   stock    165 

Lathe,    importance   of 163 

Lathe,     monitor 189 

Lathe  pans    525 

Lathe,    pit     184 

Lathe,   pulley    185 

Lathe    racks    525 

Lathe,  relationship  with  other  tools  163 

Lathe,  speed  or  hand 164 

Lathe  spindle  bearings 166 

Lathe   tail    stock 168 

Lathes,  testing  of 179 

Lathe  tools 197 

Lathe,   tool  makers 182 

Lathe  tools,  patent 200 

Lathe  tools,  patent,  advantages  of.  .  201 

Lathe  tools,   threading 203 

Lathe   tools,    setting   of 199 

Lathe,   two  spindle 183 

Lathe,    turret 186 

Lathe,  turret  chucking 188 

Lathe,     wheel 184 

Laying  out  bevel  gears 474 

Lead  screw    169-174-1 77 

Lead  screw  nut 174 

Lead  screw  threads 177 

Leather   belting    490 

Left-hand  screw  cutting 234 

Leveling    wedges    299 

Linear    velocity 463 

Line  of  action  in  gearing 473 

Link   leather  belting 496 

Lining  up  line  shafting 512 

Link  planing  attachment 295 

Limit   gauges    61 

Locating   drilled    holes 112 

Lock  nuts    451 

Lubrication    of    center    bearings.  .  .  .  222 

Lubrication  of  drills 41 

Lubricating    machine    centers 161 

Lubricating,  planer  ways 280 

Lubrication   of  milling  centers 378 

Lubrication  of  taps  and  dies 140 


M 


Machine  bolts  450 

Machinists'  cold  chisels 18 

Machine  cut  files 26 

Machinists'  hammers 17 

Mandrel  block  161 

Mandrel  centers  154 

Mandrel  centers,  care  of... 161 

Mandrel  presses  162 

Mandrels  153 

Mandrels,  driving  in  bores 161 

Mandrels,  expanding 154,  156 

Mandrels,  expansive,  advantages  of.  158 

Mandrels  for  conical  bores 158 

Mandrels  for  large  bores 159 

Mandrels,  hardened  and  ground.  . .  .  155 
Mandrels,  influence  of  on  sizes  of 

bores  156 

Mandrels,  nut 159 

Mandrels,  solid 154 

Mandrels  stub  160 

Mandrels,  taper  of 156 

Mandrels,  with  ends  only  hardened.  155 

Manufacturers'  drilling  machine.  .  406 
Measuring  machine,  Pratt  &  Whit 

ney  78 

Measuring  machine,  Rogers-Bond.  57 

Measuring  machines,  Sweets 79 

Mechanical  equivalent  of  heat 542 


Methods  for  testing  squares 95 

Method  of  lacing  belling 495 

Methods  of  lapping  belting 494 

Methods  of  producing  screw  thread*,  129 

Micrometer    calipers,    beam 76 

Micrometer  calipers,  bench 77 

Micrometer   calipers,    for   measuring 

screw  threads 73 

Micrometer  calipers,   inside 81 

Micrometer    calipers,    large '.  74 

Micrometer  calipers,  reacting  of .  .  .  !  71 

Micrometer  calipers,  use  of 

Milling   arbors    34^ 

Milling,      advantages      for      certain 

classes  of  work  over  planing.  .  312 

Milling    attachment    for    planer.  .  .  .  293 

Milling  cutters,  forms  of  teeth 345 

Milling  cutter  vibration,  causes  of.  .  378 
Milling  cutters,  advantages  of  small 

diameters  of   361-345 

Milling  cutters,  angular    336-339 

Milling  cutters,  axial 336 

Milling  cutters,  classes  of 336 

Milling   cutters,    inserted    tooth....  343 

Milling  cutters,   formed 336-339-341 

Milling  cutters,  grinding  of 345 

Milling  cutters,   method  of  driving.  346 

Milling   cutters,   nicked   teeth 337 

Milling  cutters,   radial    336 

Milling   cutters,   straddle 337 

Milling,  direction  of  feed  and  rota- 
tion of  cutter  for 358 

Milling,  examples  of 359-361-363 

Milling   head,    universal 328 

Milling  head,  vertical  spindle 328 

Milling,    in   the    lathe 260 

Milling  machine  as  a  manufacturing 

tool    313 

Milling  machine,  duplex 317 

Milling   machine   feeds 321 

Milling  machine  feeds,  all  gear....  322 

Milling  machine,  plain    314 

Milling  machine,  slabbing    317 

Milling  machine,   universal 313 

Milling  machine,  vertical  spindle.31>-319 

Milling  machines,   importance  of .  .  .  312 

Mills,    end 338 

Mills,  end,  center  cut 338 

Monitor  lathe   189 

Monkey  wrenches 100 

Movable    racks    525 

Movable  head  boring  bars   250 

Muffler  for  tempering    

Multiple  cutters,  for  boring 253 

Multiple  fluted  drills  and  their  uses.  107 

Multiple  spindle  drills .  399 

Multiple   thread   screws . .               ...  128 


Names   of  files    22,     23 

Necessity  of  belly  in  files 29 

Nut  and  washer  gauges 85 

Nut  drivers 212 

Nuts,   machine    454 

Nut    locks 452 


Object  of  tempering 440 

Odontograph.  Grant's  involute.  .      .  470 

Oil,  filtering  of 522 

Oil  pump   334 

Oil   separator    522 

Oil  tube  drills Ill 

Open  side  planer   279 

Open  side  shaper 288 

Overhanging  arm  supports 321 

Oversize  in  taps 131 


550 


INDEX. 


Parts  of  planer  head  . 281 

Patent  lathe  tools    200 

Pickling  brass  castings 47 

Pickling  castings    47 

Pilot  bars 257 

Pipe  centers    238 

Pitch    circle 465 

Pitch  of  screw  thread 127 

Planer  attachments   293 

Planer   clamps    300 

Planer  jacks   300 

Planer,   characteristic  parts    273 

Planer   and   its   modifications 273 

Planer  and  shaper  tools 291 

Planer  feeds   276 

Planer  head,  parts  of 281 

Planer,  open  side 279 

Planer,  table  drives 274 

Planer  table  reversing  mechanism.  .  275 

Planer  table  stop  pins . 302 

Plane  surface,   method  of  producing  53 

Planing,   care  necessary   in 305 

Planing,  clamping  of  work 299 

Planing,  lining  up  work 304 

Planing,   securing  work   in   vise.  .  .  .  304 

Planing,  springing  of  work  in 303 

Pneumatic  drilling  machine 518 

Pneumatic    hammers 518 

Pneumatic  hoists 517 

Pinning  of  files 45 

Plain  grinding  machine 293,  429 

Plain  milling  machine    314 

Plain  turret  screw  machine    191 

Planer   centers 296 

Planer,  jacks 300 

Planer   tool   clamps 282 

Plug   and   ring  gauges 59 

Portable  drills    405 

Portable  grinding  head 437 

Portable  key  seater   311 

Position  of  tool  for  screw  cutting.  .  233 

Position  of  work  for  filing 33 

Position  of  workman  filing 33 

Power  required  to  elevate  water.  .  .  .  542 

Power  transmitted  by  belting 493 

Pratt  &  Whitney  measuring  machine  78 
Pratt  &   Whitney's   standard  gradu- 
ated line-measure  bar 56 

Preparation  of  leather  belting 491 

Problems  in  spiral  gearing 483 

Proper  care  and  use  in  reamers.  .  .  .  122 

Pulleys 510 

Pulleys,  balancing  of 521 

Pulleys,  calculating  speed  of 514 

Pulleys,    clutch 510 

Pulley   drivers    213 

Pulley     lathe 185 

Pulley    taps    131 


u 


Rack   cutting  attachment 332,  388 

Racks,   cutting   of    388 

Rack-driven    shapers     283 

Racks   for   files    46 

Rack    teeth,    involute 469 

Racks,    movable    525 

Radial    drills    401 

Radial   mills,  advantages  of 318 

Raising    blocks 182 

Rake   angles    198 

Reamer,  special  large   421 

Reamers,    adjustable     114-120 

Reamers,  arbors  for  shell 119 

Reamers,   center   bearing 123 

Reamers,   chucking 116-118 

Reamers,    expansive    1 20 

Reamers,  fluting  of 364 

Reamers,    hand    .  116 


Reamers,  influence  of  form  and  num- 
ber  of   teeth   in 114 

Reamers,    life   of    li>0 

Reamers,  points  on  manufacture  of.  116 

Reamers,  the  proper  care  and  use  of  122 

Reamers,   shell    119 

Reamers,   solid    114 

Reamers,     stocking ]  i>2 

Reamers,  taper 120 

Reamers,  tooth  clearance   in    115 

Reamers,    undersized,    reclaiming    of  120 

Reamers    with    three    flutes 119 

Reamers  with  spiral  flutes 119 

Reaming  by   hand 124 

Reaming  in  machines    124 

Reaming   in   the   lathe 249 

Recording    calipers    64 

Regrinding  and  dressing  hammers .  .  18 
Relationship     of    lathe    with    other 

tools     163 

Relieving  attachment   for   lathes    .  .  ^4 

Reversing  drill  and  tap  holders.  ...  148 

Revolving  chucks   Ul!> 

Riveted  joints 458 

Rivet  holes    460 

Rivets     458 

Rivets,  setting  of 461 

Rogers-Bond  comparator 57 

Rogers-Bond  measuring  machine.  ...  57 

Rolled  drills    106 

Root   circle    465 

Rope  drives 502 

Rope  drives,  flexibility  of    50fr 

Rope   splicing    502 

Rope  transmissions,   systems  of.  ...  505 

Ropes,  speed  of  in  drives 507 

Round  keys   454 

Rule  for  drill  soeeds 110 

Rule  for   indexing    350 

Rules  for  determining  gear  parts  .  .  460 

Rules,   gear    94 

Rules,  hook 94 

Rules,  key  seat .  97 

Rules,   standard   steel 93 

Rules  with  end  graduation 93 


S 

Safety  edges  on  files 36- 

Scrapers  and  surface  plates 48 

Scrapers,  forms  of 48 

Scrapers,  how  held  and  used 51 

Scrapers,  use  of 48 

Scraping,  plane  surfaces 52 

Scraping,   preparation   of  work   sur- 
face for   50 

Scratch  gauges 89 

Screw  cutting,  by  use  of  compound 

rest    t 236 

Screw  cutting,  catching  thread  in ...    237 
Screw  cutting,  exercise  of  care  in.  .    235 

Screw  cutting,  in  the  lathe 233 

Screw  cutting,  left-hand 234 

Screw  cutting,  position  of  tool  for.    233 

Screw  cutting,  square  threads 236 

Screw  drives  and  how  ground 100 

Screw  machine,  plain  turret 191 

Screw  machine,  automatic 191 

Screw  thread  gauges 88 

Screw  thread,  pitch  of 127 

Screw   threads    125 

Screw  threads  table 128 

Screw  threads  for  fastenings 125 

Screw  threads  for  transmitting  mo- 
tion      125 

Screw  threads,  methods  of  producing  129 
Screw    threads,    square,    trapezoidal 

and  Powell's 127 

Screws,  cap   452 

Screws,   set    453 

Securing   work   on   planer 299,  304 

Securing  work  to  knee  plate 254 


INDEX. 


551 


Selecting  files  for  any  class  of  work 

30,  34,  40 

Self-hardening  steel   200 

Self-opening  dies 138 

Sellers'  planer  table  drive 2i4 

Sensitive  drills 397 

Shaper  attachments    283-21)7 

Set   screws    453 

Setting  of  lathe  tools v. .  .  .  .    199 

Setting  of  rivets 461 

Setting  tool  for  taper  turning 231 

Setting  up  work  for  boring 253 

Shaft,   bearing    511 

Shaft,  couplings   508 

Shafting,  alining    512 

Shaper,  draw  stroke 289 

Shaper,  movable  head 289 

Shaper,   open   side 288 

Shapers,  characteristic  parts 282 

Shapers,    crank    driven 283 

S*apers,  rack  driven 283 

Sheaves,  rope    506 

Shell  reamers   119 

Shrink  fit,  definition  of 262 

Single  cut  files   25 

Slabbing  cutter   343 

Sleeves,  drill   144 

Slide  rest 170 

Slotted  link,  for  shaper 284 

Slotting  attachment 334 

Slotting  machine    306 

Slotting  machine  work,  example  of.  .    307 

Sockets,  drill 142 

Sockets,  special  form  of  drill 144 

Sockets  for  oil  tube  drills 248 

Sockets,  frictional  driven 147 

Sockets,    grip     145 

Sockets,  lathe   145 

Solid  dies 136,  138 

Solid  mandrels 154 

Solid  reamers 1 

Special   form  of  drill  sockets 144 

Special     tool     for    planing    circular 

surfaces      296 

Speeds  for  milliner  cutters 356 

Spherical    turning    243 

Spherical   socket  boring    261 

Speed   of  emery   wheels 430 

Speed  of  hand  lathe   164 

Spindle   ends   squaring  off 223 

Spiral  cutting  attachment    332 

Spiral,   cutting  of  a 354 

Spiral  gears    467 

Spring  for  planer   tools    292 

Spring  joint  calipers 65 

Spiral  gears,   data  for 482 

Spiral  gears,  elements  of 479 

Spiral  geared  planer 276 

Spiral  gearing,  problems  in 483 

Spiral  gears,  cutting  of 394 

Spirals,  calculations  for  the  change 

gears    354 

Spur  gears    467 

Square,    box 97 

Square   corner   filing 37 

Squares,   combination    96 

Squares,  methods  for  testing 95 

Squares,     standard    steel 94 

Squares,   thin    steel 96 

Squaring  off   spindle   ends 223 

Standard   gauges    59 

Standard     graduated       line-measure 

bar.  Pratt  &  Whitney    56 

Standards   of   measurp    : 55 

Standard  pattern  drilling  machines.    397 

Standard  steel  rules   93 

Standard  steel  squares 94 

Standard  thread  gauges    62 

Straightening   of   tempered   work .  .  .    445 

Straight   edires.    cast    iron    98 

Straight  edges,  steel 97 

Stay    bolts     461 

Stay  bolt  taps 132 


Stays,    crown    sheet     462 

Stays,     diagonal     '. 461 

Steady    rest    L'25 

Steel,  air  hardening  tool    447 

Steel,  effect  of  carbon  in   44O 

Steel   hardening    44O 

Steel,  heating  of   441 

Steel,    quenching   of    443 

Steel,    self-hardening    tool    447 

Stock,  keeping  of 524 

Stops,    milling   machine   table .",75 

Stud    bolts    451 

Stud  set 451 

Supporting  work   not   round 226 

Surface   disc   grinder    436 

Surface  file  holders 32 

Surface  gauge,  use  of 221 

Surface  grinder    435 

Surface    plates    50-54 

Surface   plates,   care   of 54 

Sweep    cutter    419 

Sweep   drilling    415 

Sweet's  measuring  machines    79 

Systems   of   rope   transmission 505 


Table    of    capacities    of    rectangular 

tanks    541 

Table  of  capacities  of  round  tanks.    541 
Table     of      circumferences,       areas, 

squares,  etc.,  of  circles 529 

Table  of  cycloidal  gear  cutters.  .  .  .   382 

Table   of  decimal   equivalents 520 

Table  of  dimensions  of  keys  and  key 

ways     '.   527 

Table  of  drill   speeds 110 

Table  of  emery  wheel   speeds 536 

Table  feeds  on  milling  machines    .  .    321 

Table  of  gas  tap  sizes 133 

Table   of   horse   power   of   transmis- 
sion rope   538 

Table  of  involute  gear  cutters 381 

Table  of  machine  screws   537 

Table  of  metric  conversions 542 

Table  of  milling  speeds 357 

Table  of  properties  of  metals 533 

Table  of  relative  values  of  non-con- 
ductors         533 

Table  of  size  of  tap  drills 537 

Table  of  screw   threads 128 

Table  of  sizes  of  chimneys  with  ap- 
proximate horse  power  boilers.    541 
Table  of  specific  gravity  and  weight 

of  various   metals 532 

Table  of  speed  of  drills 536 

Table     of     standard    dimensions    of 
wrought    iron    steam,    gas    and 

water  pipes 534 

Table     of    different     standards     for 

wire  gauge  in  the  U.   S 528 

Table  of  standard  hexagon  bolts  and 

nuts    535 

Table  of  tap  drill  sizes  for  gas  pipe  537 

Table  of  tap  drill  sizes 112 

Tables  for  transmitting  efficiency  of 

turned   shafting    539 

Tables  of  transmission  of  power  by 

leather  belting   538 

Table  of  units  of  heat  in  one  pound 

of  fuels    533 

Table  of  weight  of  flat  bar  iron.  .  .  .    53t 

Table  of  weight  of  plate  iron 531 

Table    of    weight    of    castings    from 

patterns    533 

Table    of    weights     of    square    and 

round  bars  of  wrought  iron.  .  .  .    53O 
Table    of    weight    of    various    sub- 
stances        532 

Table  feed  rack,  dangers  of 321 

n   pnd   df»   action   when   dull....    141 
Tap  drill  sizes 112 


552 


INDEX. 


Tap  drill  sizes,  how  found 141 

Tap  holders,  frictional  147-149 

Tap  wrenches 151 

Taper  attachment  189 

Taper  drill  shanks 108 

Taper  grinding  431 

Taper  keys  455 

Taper  milling  376 

Taper  pins  458 

Taper  reaming  122 

Taper  turning 226-229-232 

Taper  turning  attachment  230 

Taper  turning  lathe 231 

Taper  turning  with  compound  rest.  231 
Taper  turning,  setting  of  tool  for.  .  231 

Tapers,  Brown  &  Sharpe  346 

Taps,  care  in  the  use  of 134 

Taps  collapsing  133 

Taps,  combination  drill  and  pipe.  .  133 

Taps,  form  of  flutes  and  teeth 131 

Taps,  hand  129 

Taps,  hob  and  pipe 132 

Taps,  pulley  131 

Taps,  square,  starting  of 135 

Taps,  stay  bolt  132 

Taps,  taper,  plug  and  bottoming.  .  130 
Taps,  use  of  two  on  heavy  tapping  135 

Temper,  drawing  of  in  sand 445 

Temper  of  twist  drills 107 

Tempered  work,  straightening  of .  .  .  445 

Tempering  by  color 444-447 

Tempering  in  oil  444 

Tempering,  object  of 441-443 

Tempering  of  steel  ._. 440 

Tempering,  warping  of  articles  in.  .  445 

Testing  of  lathes 179 

Thread  calipers  68 

Three  flute  drills 107 

T  slot  cutters  339 

Tool  grinder  424 

Tool  clamps,  planer 282 

Tool,  for  planing  key -ways 291 

Tool  setting,  influence  of  on  taper 

turning  227 

Tool,  special ,  for  planing  circular 

surfaces    .  .    296 


Tools  for  slotting  machine..  ..    308 

Tools,  spring  for  planer   ....  .  .    292 

Tools,   finishing  for   planer.  .  .  .    293 

Tools,    under    cut    for    planer          .  .    292 

Toothed   gears    464 

Tote   boxes    525 

Transmission   of  electric   power.  .  .  .    515 
Transmitting     motion      for      screw 

threads     125 

Turning  a  plain  spindle   220 

Turning  cams   246 

Turning    concave    and    convex    sur- 
faces         245 

Turning    cross-head    pins 239 

Turning   crank    pins    232 

Turning,   exercise  of  judgment   in.  .    224 

Turning  irregular   outlines 242-245 

Turning    long   work   by    use    of   hol- 
low rest 227 

Turning,    offset    work 232 

Turning   shafting    239 

Turning  spherical  work    243 

Turning  taper   work    226-229-232 

Turret    boring,    example    of 257 

Turret   chucking   lathe,   automatic..    192 

Turret    chucking    lathes 192 

Turret  drilling  machines 403 

Turret    facing,    example   of 257 

Turret  machine  operations 256 

Turret,    on    carriage    186 

Turret  on  shears   . 188 

Turret    tools    195-207 

Turret  work,  examnl^  of  heavy....    258 
Twist   drill    cutting   in    milling   ma- 
chine    ...  368 


Twist    drill    grinder 428 

Twist    drills    io,> 

Twist  drill,  relieving  of   369 

Two   classes  of  dies 135 

Two  spindle  lathe 183 


U 

United   States   standard   of  measure     55 

United  States  standard  thread 125 

Universal  boring  mills    269 

Universal  chucks   215 

Universal   drilling   tables '.'..   403 

Universal    grinding    machine 428 

Universal    indexing   head 325 

Universal   milling  head 328 

Universal    milling    machine 313 

Unit  of  heat 542 

Unit  of  work    542 

Use    of   calipers    65,     67 

Use  of  center  head   square 221 

Use  of  chalk  and  oil  on  files 45 

Use  of  gauges 61 

Use     of    graduated     dials     on     feed 

screws    362 

Use  of  knee  plate 375 

Use  of  micrometer  calipers   72 

Use  of  oil  tube  drills   248 

Use  of  scrapers    48 

Use  of  surface  gauge    221 

Use  of  test  indicator    .  92 


Value  of  graduated  machine  dials..  378 

V  blocks    303 

V  threads    125 

Velocity    ratio     466 

Velocity    ratio   in    elliptical    gearing  466 

Vernier  calipers,  reading  of 69 

Vertical    boring    mills     264 

Vertical  milling,  examples  of 370 

Vise,    drilling    - 408 

Vise   jaws,    soft 38 

Vise   jaws,    spring 38 

Vise,  jig  drilling 409 

Vise  jigs 38 

Vises,  milling  machine   327 

Vises,    planer    295 

Vise,    planer   and     shaper,     securing 

work  in    304 

Vises,   special   jaws  for    372 

Vises,  use  of  two  in  milling 371 


W 

Warping  of  articles  in  tempering  .  .  445 

Waste  cans   523 

Water,   data   on 542 

Water,  power  required  to  elevate..  542 

Weight  of  hammers 17 

Whitworth    quick    return    motion    .  .  280 

Whitworth   standard   thread    125 

Wire   belt    lacing 495 

Wire  gauges,   comparison  of 82 

Work   supports    224 

WTork,  unit  of 542 

Work,   securing  of  on  planer...    299-304 

Working  fit,  allowance  for 262 

Working  fit.  definition  of 262 

Worm  gears,  cutting  of   365 

Worm  gears,  forms  of  teeth    477 

Wrenches,  box,  socket  and  ratchet .  .  102 

Wrenches,  combination    102 

Wrenches,   correct   use   of  monkey..  10O 

Wrenches,    monkey    100 

Wrenches,  solid  15  degree   102 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


MAR     3  1943 


MaW9f1     l-OAN  DEPT. 


9NOV53SS 


>2s) 


\ 


REC'D 


40390 


X 


